JPH0830433B2 - Internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention is mainly applied to the extent that one intake valve is put into a substantially idle state during an intake stroke in a low speed operation range of an engine. A valve operating device configured to open only a small amount and connected to a pair of intake valves, and a fuel injection valve capable of uniformly injecting fuel toward a confluence of a pair of intake ports individually corresponding to both intake valves. , And a control means for controlling the operation of the fuel injection valve.

(2) Conventional Technology Conventionally, one of a pair of intake valves is lifted by a small amount in the engine low speed operation range to prevent an increase in fuel consumption in the engine low speed operation range and to be substantially closed. An internal combustion engine which avoids fuel accumulation in a port to achieve stable combustion is disclosed, for example, in Japanese Utility Model Laid-Open No. 60-195913.

(3) Problems to be Solved by the Invention When one intake valve is placed in a substantially resting state as in the conventional one described above, the air-fuel mixture flows into the combustion chamber from substantially only the other intake valve side. It is possible to form a swirl in the combustion chamber. By the way, if the fuel concentration is changed along the axial direction in the combustion chamber to perform the axial stratified charge so as to form the rich zone having a relatively high fuel concentration around the spark plug, the combustibility may be improved. A combination of the swirl formation and the axial stratified charge, which has been conventionally known, will further improve the combustibility and enable stable lean combustion.

However, in an operating state in which one intake valve is in a substantially resting state, it is possible to perform axial stratified charge only when the fuel injection timing by the fuel injection valve is a specific timing. Became clear by.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an internal combustion engine that enables axial stratified charge in an operating state in which one intake valve is in a substantially resting state and has improved combustibility.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the invention described in claim 1, one intake valve is mainly used in the intake stroke in the low speed operation range of the engine. A valve operating device that is configured to open only a minute amount that is substantially in a rest state and is connected to a pair of intake valves, and fuel is evenly directed toward a pair of intake ports individually corresponding to both intake valves. In an internal combustion engine including an injectable fuel injection valve and a control means for controlling the operation of the fuel injection valve, the control means controls the fuel injection end timing during the intake stroke when one of the intake valves is in a substantially idle state. Is configured to control the fuel injection valve.

According to the invention as set forth in claim 1, a pair of intake valves is constructed so as to open only one intake valve by a very small amount that is substantially in a resting state in the intake stroke in the low speed operation range of the engine. A fuel injection valve capable of uniformly injecting fuel toward a pair of intake ports individually corresponding to both intake valves, and a control means for controlling the operation of the fuel injection valve. In an internal combustion engine capable of lean combustion in an engine operating range in which at least one of the intake valves is in a substantially resting state, a concave portion forming a part of the combustion chamber is provided on a surface of the piston facing the combustion chamber. The valve operating device is configured such that the opening angle center timing of the one intake valve in the substantially resting state is in the latter half of the intake stroke, and the control means is such that the one intake valve is in the substantially resting state. Sometimes the fuel injection end timing is set in the first half of the intake stroke. Configured to control the Umate fuel injection valve.

Further, according to the invention described in claim 1, the intake valve is connected to the pair of intake valves and the pair of exhaust valves, and one of the intake valves is put into a substantially idle state mainly in the intake stroke in the low speed operation range of the engine. A valve operating device configured to open only a small amount, a fuel injection valve capable of uniformly injecting fuel to a pair of intake ports individually corresponding to both intake valves, and operation control of the fuel injection valve A combustion chamber in which an ignition plug is arranged substantially in the center of the ceiling surface in an internal combustion engine capable of performing lean combustion in an engine operating region in which at least one of the intake valves is in a substantially idle state. Is provided on the upper surface of the piston facing the
The valve train has a single camshaft that is common to both intake valves and exhaust valves, and is configured so that the center angle of opening of one intake valve in the substantially rest state is in the latter half of the intake stroke. The means is configured to control the fuel injection valve by setting the fuel injection end timing in the first half of the intake stroke when the one intake valve is in the substantially idle state.

(2) Operation According to the configuration of the invention as set forth in the above-mentioned claim, the fuel injection by the fuel injection valve when one of the intake valves is in the substantially idle state is ended during the intake stroke, so that the fuel injection valve It is possible to achieve the axial stratified charge by sequentially introducing the fuel injected from the fuel injection chamber into the combustion chamber with the other intake valve opened.

According to the configuration of the invention described in claim 1, when one of the intake valves is in the substantially idle state, the fuel injected from the fuel injection valve is sequentially introduced into the combustion chamber while the other intake valve is open. Axially stratified charge can be achieved, and by providing a recess on the upper surface of the piston, it is possible to promote combustibility improvement by increasing swirl speed associated with the formation of a compact combustion chamber. The torque fluctuation can be suppressed because the injection end timing is in the first half of the intake stroke, and the opening angle center timing when one intake valve is in a substantially resting state is in the latter half of the intake stroke. It is possible to suppress the occurrence of swirl turbulence due to a slight opening of the valve.

Further, according to the configuration of the invention described in the above claim,
When one of the intake valves is in a substantially rest state, the fuel injected from the fuel injection valve can be sequentially introduced into the combustion chamber while the other intake valve is open to achieve axial stratified charge. With the provision of a common single camshaft for both intake valves and exhaust valves, and the provision of a recess in the upper surface of the piston facing the combustion chamber in which the spark plug is disposed approximately in the center of the ceiling surface. , It becomes possible to form a more compact combustion chamber, it is possible to promote the improvement of combustibility by increasing the swirl speed associated with making the combustion chamber compact, and furthermore, the fuel injection end timing is in the first half of the intake stroke. Torque fluctuation can be suppressed, and the swirl turbulence that accompanies a slight opening of one intake valve can be generated by setting the center angle of opening angle of one intake valve in the actual rest state to the latter half of the intake stroke. It can be suppressed.

(3) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

1 to 8 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram, FIG. 2 is an enlarged plan view of a partial notch along line II-II of FIG. FIG. 3 is a diagram showing a relationship between an intake valve operating state and fuel injection timing, FIG. 4 is a flow chart showing a procedure for executing feedback control, and FIG. 5 is an experimental result of influence of fuel injection timing on combustion stability. FIG. 6 is a graph showing the experimental results of the influence of the fuel injection end timing on the torque fluctuation rate, and FIG. 7 is an experiment of the influence on the combustion limit by the opening angle central timing of the intake valve in the substantially idle state. FIG. 8 is a graph showing the result, and FIG. 8 is a graph showing the experimental result of the influence on the torque fluctuation rate, the fuel consumption, and the exhaust gas property depending on the difference in the center timing of the opening angle of the intake valve in the substantially resting state.

First, in FIG. 1, a cylinder head 2 is connected to an upper surface of a cylinder block 1 and upper surfaces of a plurality of cylinders 3 provided in the cylinder block 1 are formed so as to constitute a main part of an engine body in a SOHC type multi-cylinder internal combustion engine. Cylinders 4 each having a recess 4a are slidably fitted therein, and combustion chambers 5 are formed between the upper surfaces of the pistons 4 and the cylinder head 2.

A pair of intake valve openings 6 and a pair of exhaust valve openings 7 are provided in the cylinder head 2 so as to open to the ceiling surface of the combustion chamber 5. Further, in the cylinder head, a pair of intake ports 8 branching from a single intake opening end 9 opening on one side surface thereof and connected to the pair of intake valve openings 6 individually, and a pair of exhaust ports 7 individually connected to the exhaust valve openings 7. And a pair of exhaust ports 10 connected in common to a single exhaust opening end 11 opened on the other side surface of the cylinder head 2. A pair of intake valves V _I1 , V _I2 that can open and close both intake valve ports 6 individually are
Intake valves that are slidably fitted in a pair of guide cylinders 12 arranged in the
V _I1, coiled valve spring 14 surrounding the intake valves V _I1, V _I2 between respectively fixed retainer 13 and the cylinder head 2 to the upper end of the V _I2 is interposed respectively, their valve The springs 14 urge the intake valves V _I1 and V _I2 upward, that is, in the valve closing direction. Further, a pair of exhaust valves V _E1 and V _E2 capable of opening and closing the two exhaust valve ports 7 individually are slidably fitted to a pair of guide cylinders 15 arranged in the cylinder head 2, respectively. Retainer 16 and cylinder head 2 fixed to the upper end of each exhaust valve V _E1 and V _E2 protruding from cylinder 15.
And a coil-shaped valve spring 17 surrounding the exhaust valves V _E1 and V _E2 , respectively, are interposed between the exhaust valves V _E1 and V _E2 . Energized.

Referring also to FIG. ₂ , a valve train 18 is connected to both intake valves V _I1 , V _I2 and both exhaust valves V _E1 , V _E2 . The valve operating device 18 rotates a single camshaft 19 linked to a crankshaft (not shown) at a speed reduction ratio of 1/2 and rotational movement of the camshaft 19 to open and close the intake valves V _I1 and V _I2 . First and second intake side rocker arms 20, 21 for conversion into
And the rotational movement of the camshaft 19 is controlled by the two exhaust valves V _E1 and V _E2.
And the first and second exhaust side rocker arms 22 and 23 for converting into the opening / closing movement of the.

The camshaft 19 includes a cylinder head 2 and holders 24 that are respectively coupled to the cylinder head 2 on both sides of the cylinder 3 along the axis of the crankshaft 19 and have a horizontal axis perpendicular to the axis of the cylinder 3. While being rotatably supported.

The camshaft 19 includes an intake side cam 25 and an intake side cam 25.
A raised portion 26 adjacent to one side of 25 is integrally provided, and exhaust side cams 27, 27 are integrally provided on both sides of the intake side cam 25 and the raised portion 26. The raised portion 26, one V _I2 of the intake valves V _I1, V _I2 mainly at low speed operating range of the engine
Is basically the camshaft 19 so that the
Although it is formed to have a circular outer surface centered on the axis line of the above, a slightly projecting protrusion is provided at a position corresponding to the high position of the air supply side cam 25. Moreover, the width of the raised portion 26 in the direction along the axis of the camshaft 19 is set to be relatively narrow.

The one of the intake valves V _I1 is the first intake-side rocker arm 20 interlocking is connected, the other intake valve V _I2 second intake-side rocker arm 21 is linked, coupled, the intake-side rocker arm 20, 2
1 is a position diagonally above the camshaft 19
An intake side rocker shaft 28 fixedly supported by a holder 24 while having an axis parallel to 9 is swingably supported.
Both exhaust side rocker arms 22 and 23 are connected to both exhaust valves V _E1 and V _E2.
And an exhaust side rocker shaft fixedly supported by a holder 24 in parallel with the intake side rocker shaft 28 at a position diagonally above the camshaft 19 in parallel with each other.
It is rockably supported on 29.

The intake side cam 25 is provided at one end of the first intake side rocker shaft 20.
A roller 30 that is in sliding contact with is rotatably supported, and at one end of the second intake-side rocker arm 21, a sliding contact portion 31 that is in sliding contact with the raised portion 26 is provided.
Corresponding to, the width is narrowed. A roller 32, which is in sliding contact with the exhaust side cams 27, 27, is pivotally supported at one end of each of the exhaust side rocker arms 22, 23.

The other end of each of the first and second intake-side rocker arms 20 and 21 has a tappet screw 33 that abuts on the upper ends of both intake valves V _I1 and V _I2.
Are respectively screwed so as to be able to move back and forth, and the intake valves V _I1 and V _I2 are opened and closed according to the swinging operation of both intake side rocker arms 20 and 21. Also, both exhaust side rocker arms 22,2
A tappet screw 34, which abuts on the upper ends of the exhaust valves V _E1 and V _E2 , is screwed at the other end of 3 so that the exhaust valves V _E1 and V _E2 can freely move back and forth. valve
V _E1 and V _E2 will open and close.

Both intake valves V _I1 and V _I2 are attached to both intake side rocker arms 20 and 21.
In order to switch the operating characteristics of the engine mainly between the low speed rotation range of the engine and the high speed rotation range of the engine, the connection state of both intake side rocker arms 20, 21 and both intake side rocker arms 2
Valve operating characteristic switching means 35 capable of switching the connection release state of 0, 21
Is provided.

This valve operating characteristic switching means 35 is provided on both intake side rocker arms.
Connection piston 36 that can connect 20, 21 and connection piston 36
And a return spring 38 that urges the connecting piston 36 and the restricting member 37 toward the disconnection side.

The connecting piston 36 is slidable on the first intake-side rocker arm 20 while defining a hydraulic chamber 39 between one end thereof and the first intake-side rocker arm 20 so as to be movable in the axial direction parallel to the intake-side rocker shaft 28. It is possible to be fitted. A communication passage 40 communicating with the hydraulic chamber 39 is formed in the first intake-side rocker arm 20, and the communication passage 40, that is, the communication passage 40, is formed in the intake-side rocker shaft 28 regardless of the swinging state of the first intake-side rocker arm 20. An oil passage 41 (see FIG. 1) that is in constant communication with the hydraulic chamber 39 is provided. As shown in FIG. 1, the oil passage 41 is connected to a hydraulic pressure source 43 via a connection switching electromagnetic control valve 42.

The connecting piston 36 is attached to the second intake-side rocker arm 21.
A closed-end cylindrical regulation member 37 whose closed end is in contact with the other end of the is fitted slidably. Further, the return spring 38 is contracted between the second intake side rocker arm 21 and the regulating member 37, and the connecting piston 36 and the regulating member 37, which are brought into contact with each other by the spring force of the return spring 38, move toward the hydraulic chamber 39 side. Be energized.

In the characteristic switching means 35 for such valve operation, the hydraulic pressure in the hydraulic chamber 39 is released mainly by the connection switching electromagnetic control valve 42 in the low speed operation range of the engine, and the spring force of the return spring 38 causes the connection piston 36 and the regulating member. The contact surface of 37 is located between the first and second intake-side rocker arms 20, 21. Therefore, both intake side rocker arms 20 and 21 are in a state capable of relative angular displacement with respect to each other, and the rotation operation of the cam shaft 19 causes the first intake side rocker arm 20 to swing in response to the sliding contact with the intake side cam 25. Intake valve V _I1 of intake side cam 25
It opens and closes at the timing and lift according to the shape of. In addition, the second intake side rocker arm 21 that slidably contacts the raised portion 26.
Becomes substantially inactive, and the other intake valve V _I2 can be substantially inactive. Moreover, the intake valve V _I2 does not completely rest, but when one intake valve V _I1 opens, it operates slightly in the opening direction, so the intake valve V _I2 that occurs when the valve is completely closed. Can be prevented from sticking to the valve seat and fuel can be prevented from staying. Further exhaust valve
V _E1 and V _E2 are opened and closed with the timing and lift amount according to the shape of the exhaust side cams 27, 27.

By the way, when the lift profile of the intake valve V _I1 by the intake cam 25 is as shown by the curve A in FIG. 3 (a), the lift profile of the intake valve V _I2 slightly opened by the raised portion 26 is The curve B in FIG. 3 (a) shows that the opening angle center timing θ _C is in the latter half of the intake stroke when the intake valve V _I1 is open, preferably the intake stroke starts. It is set in the range of 130 to 180 degrees from TDC. Moreover, the closing timing θ _VC of the intake valve V _I2 that is slightly opened by the raised portion 26 is the buffer curve of the end portion along the crank angle in the lift profile of the intake valve V _I1 shown by the curve A in the intake side cam 25. Part A _SC , that is, the part corresponding to the operation profile of the intake valve V _I1 corresponding to the transition part from the high position to the base circle part of the intake side cam 25 in order to mitigate the impact when the intake valve V _I1 is seated It is what is done. The lift amount of the intake valve V _I2 is set to, for example, about 0.4 to 2.0 mm.

Further, mainly during high-speed operation of the engine, the connection switching electromagnetic control valve 42 is opened to apply high hydraulic pressure to the hydraulic chamber 39. As a result, the connecting piston 36 tries to move in the direction of increasing the volume of the hydraulic chamber 39 against the spring force of the return spring 38, and when the axes of the connecting piston 36 and the regulating member 37 coincide, that is, both intake side rocker arms 20. , 21 enters the stationary state, the connecting piston 36 fits into the second intake side rocker arm 21, both intake side rocker arms 20, 21 are in the connected state, and the first intake side is in sliding contact with the intake side cam 25. The second intake side rocker arm 21 swings together with the rocker arm 20, and both intake valves V
_I1 and V _I2 are the timing and lift amount according to the shape of the intake cam 25 (the profile shown by the curve A in FIG. 3 (a))
It can be opened and closed with. Also, both exhaust side rocker arms 2
2 and 23 open and close both exhaust valves V _E1 and V _E2 at the timing and lift amount according to the shape of the exhaust side cams 27 and 27 as in the low speed operation range.

The cylinder head 2 has rocker arms 22 and 23 on both exhaust sides.
A plug tube portion 44 is provided so as to incline sideways as it goes upward between them, and an ignition plug 45 inserted from this plug tube portion 44 has a cylinder head 2 at a substantially central portion of the ceiling surface of the combustion chamber 5. Mounted on.

Referring again to FIG. 1, an air cleaner 49 is connected to the intake opening end 9 of the cylinder head 2 via an intake manifold 46 and a throttle body 48 having a throttle valve 47. An intake passage 50 is formed in the throttle body 48 and the intake manifold 46 between the air cleaner 49 and the intake opening end 9, and the intake passage 50 has a bypass passage 51 and a first idle passage 52. Throttle valve 47
A bypass electromagnetic control valve 53 is provided in the bypass passage 51, and a wax valve 54 that operates according to the cooling water temperature of the engine body is provided in the first idle passage 52. It

At the end of the intake manifold 46 on the cylinder head 2 side, a fuel injection valve 55 is attached to inject fuel evenly from the intake opening end 9 toward both intake ports 8, and the fuel injection valve 55 is supplied with fuel. Source 56 is connected.

The fuel injection valve 55 is configured to be able to controllably inject the fuel supplied from the fuel supply source 56 and to inject assist air for atomizing the injected fuel. A passage 57 for supplying the assist air is connected to the fuel injection valve 55. Thus the passage
57 is connected to the air header 58 common to each cylinder,
The air header 58 is connected to the intake passage 50 on the upstream side of the throttle valve 47 via the electromagnetic air amount control valve 59 and the idle adjusting screw 60.

A catalytic converter 62 is connected to the exhaust opening end 11 of the cylinder head 2 via an exhaust manifold 61, and an exhaust gas sensor 63 capable of linearly detecting the O ₂ concentration in the exhaust gas is attached to the exhaust manifold 61.

Electromagnetic control valve 42 for switching the connection, electromagnetic control valve for bypass
The operations of the fuel injection valve 53, the fuel injection valve 55, and the electromagnetic air amount control valve 59 are controlled by a control means 67 composed of a computer, and the control means 67 includes an intake pressure P detected by an intake pressure sensor 64. _B , the cooling water temperature T _W detected by the engine cooling water temperature sensor 65, and the engine speed N _E detected by the rotation speed sensor 66 are input, and an exhaust gas sensor for performing feedback control during lean combustion of the engine. 63 detection values are input.

And Thus, the control unit 67, a decoupling state the intake side rocker arm 20, 21 so as to substantially pause one V _I2 of the intake valves V _I1, V _I2 when the engine is in the low rotational speed range mainly At the same time, when the engine is mainly in the high speed rotation range, the valve operation characteristic switching means 35 is operated so that both intake side rocker arms 20 and 21 are connected to open and close both intake valves V _I1 and V _I2 by the intake side cam 25. In addition, when the engine is mainly in the low speed rotation range, that is, when one of the intake valves V _I1 and V _I2 , V _I2, is substantially in the idle state, the fuel injection timing of the fuel injection valve 55 is set as shown in FIG. ), The fuel injection end timing θ _FE is during the intake stroke, and it is desirable that the first half of the intake stroke, for example, from the intake stroke start TDC to 5
The control is performed so that the range is 0 to 90 degrees.

Further, the control means 67 controls the fuel injection amount from the fuel injection valve 55 so as to perform lean combustion when the engine is mainly in the low speed rotation range, and at the time of the lean combustion, the exhaust gas sensor follows the procedure shown in FIG. The feedback control of the fuel injection amount is performed based on the detection value of 63.

In FIG. 4, in the first step S1, the exhaust gas sensor 63
Is read, and it is determined in a second step S2 whether the engine is in the starting state. Thus, in the engine starting state, the routine proceeds from the second step S2 to the third step S3, and in this third step S3, the correction coefficient K _LAF used in the calculation of the fuel injection amount described later is set to "1.0", and the next After the target air-fuel ratio is set to the engine starting air-fuel ratio in the fourth step S4, the fuel injection amount is calculated in the fifth step S5.

In calculating the fuel injection amount in this fifth step S5,
Actually, the injection time T _I of the fuel injection valve 55 is based on the following formula (1).

T _I = T _IM × K _CMDM × K _LAF × K _I + C (1) In this formula (1), T _IM is the basic injection time preset based on the engine speed N _E and the intake pressure P _B. And K _CMDM is a correction coefficient for correcting the target air-fuel ratio preset based on the engine speed N _E and the intake pressure P _B by the intake air amount, and basically (T _IM × K _CMDM ). Thus, the injection time for the target air-fuel ratio can be obtained. Also K
_LAF is a correction coefficient for feedback control according to the detection value of the exhaust gas sensor 63, and when "1.0", the feedback control is not executed. Further, K _I is a correction coefficient based on the water temperature and the atmospheric pressure, and C is a correction coefficient based on the battery voltage and the vehicle acceleration that affect the fuel injection operation of the fuel injection valve 55.

In the sixth step S6, the fuel injection start timing is calculated in consideration of the engine speed N _E so that the fuel injection end timing θ _FE is within the intake stroke, preferably in the first half of the intake stroke.
In step S7, the fuel injection time T _I, that is, the fuel injection amount is output at the timing calculated in the sixth step S6.

When it is determined in the second step S2 that the engine has transitioned from the starting state to the normal operating state, the process proceeds from the second step S2 to the eighth step S8. In the eighth step S8, the engine speed N _E and the intake air The target air-fuel ratio is calculated on the basis of the pressure P _B using a preset map. Then, in the next ninth step S9, it is judged whether or not the exhaust gas sensor 63 is in the active state. This is to determine whether the exhaust gas sensor 63 is in a state where it can exhibit a normal detection function, for example, by determining the temperature of the exhaust gas sensor 63, and when it is determined that the exhaust gas sensor 63 is not in the active state, the correction coefficient in the tenth step S10. 5th step S after K _LAF is set to "1.0"
When it is determined that the operation state is the active state, the operation proceeds to the eleventh step S11.

In the eleventh step S11, the actual air-fuel ratio is calculated based on the detection value of the exhaust gas sensor 63. That is, the exhaust gas sensor 63
Outputs a voltage linearly according to the O ₂ concentration in the exhaust gas, and the actual air-fuel ratio is calculated based on a table preset corresponding to the voltage.

In the twelfth step S12, it is determined whether or not the feedback control is possible. That is, feedback control based on the detection value of the exhaust gas sensor 63 is performed when fuel cut is being performed by engine speed control, vehicle speed control, traction control, etc., and immediately after the fuel cut is performed. Is meaningless, and when the engine cooling water temperature T _W is extremely low, atomization of the injected fuel is insufficient and fuel adheres easily to the inner surface of the intake port 8. Therefore, based on the detection value of the exhaust gas sensor 63, The actual air-fuel ratio obtained indicates that the fuel concentration is low,
If the feedback control is executed in such a state, the fuel concentration becomes unnecessarily high. Therefore, when the fuel cut is being performed, immediately after the fuel cut is performed, and when the engine cooling water temperature T _W is extremely low, the feedback control is prohibited and the process proceeds from the twelfth step S12 to the tenth step S10. In case of, it is assumed that the feedback control is executed, and the process proceeds from the 12th step S12 to the 13th step S13.

In the 13th step S13, the correction coefficient K _LAF is calculated based on the difference between the target air-fuel ratio and the actual air-fuel ratio, and the next 14th step
In S14, it is judged whether the calculated correction coefficient K _LAF is within a certain range, and if it exceeds the range, a predetermined maximum value or minimum value is set to the correction coefficient K _LAF.
It is output as _LAF , and the fuel injection amount is calculated in the fifth step S5.

Next, the operation of this embodiment will be described. When the engine is mainly in the high speed rotation range, the control means 67 connects both intake side rocker arms 20, 21 by the valve operating characteristic switching means 35, and the valve operating device 18 operates both The intake valves V _I1 and V _I2 are opened and closed at the timing determined by the intake cam 25 and the lift amount.

Further, when the engine is mainly in the low speed rotation range, the valve operating characteristic switching means 35 is switched by the control means 67 to a state where the connection between the intake side rocker arms 20 and 21 is released. Thus, one V _I2 of the intake valves V _I1, V _I2 is substantially become dormant, only the other intake valve V _I1 is made to opened and closed with a timing and a lift amount determined by the intake cam 25.

As a result, in the combustion chamber 5, substantially both intake valve ports 6
The air-fuel mixture will flow in from only one side of the combustion chamber 5
A swirl will be formed inside. Moreover, the fuel injection by the fuel injection valve 55 at the time of generating the swirl is controlled so as to be ended during the intake stroke, and the injected fuel is burned from the intake valve port 6 corresponding to the intake valve V _I1 which is opening and closing. It is possible to successively introduce the gas into the chamber 5 to achieve the stratified charge in the axial direction, and the combustibility can be improved as shown in FIG. 5 showing the experimental result of the present inventor.

Further, the fuel injection end timing θ _FE by the fuel injection valve 55 is the third
As shown in Figure (b), the first half of the inhalation stroke is preferably set in the range of 50 to 90 degrees from the inhalation stroke start TDC, and when such setting is made, the sixth experimental result of the present inventor is shown. As shown in the figure, the torque fluctuation rate can be suppressed small.

Furthermore, the intake valve V _I2 which is slightly opened by the raised portion 26
As shown by the curve B in Fig. 3 (a), the center angle θ _C of the opening angle is in the intake stroke, and the latter half of the intake stroke is preferably started.
It is set in the range of 130 to 180 degrees from TDC, and if set in such a range, it becomes possible to suppress the occurrence of swirl turbulence due to the slight opening of the intake valve V _I2 . Thus, the experimental results of the combustion limit with respect to the opening angle central timing θ _C are shown in
As shown in the figure, it is apparent that the lean combustion limit is improved by setting the latter half side of the open angle center timing θ _{C in the} intake stroke, preferably in the range of 130 to 180 degrees from the intake stroke start TDC. Further, FIG. 8 shows the results of experiments conducted by the present inventor regarding the influence on torque fluctuation and fuel consumption due to the difference in the opening angle central timing θ _C , as shown in FIG. 8, in which the opening angle central timing θ _C is set at the center of the intake stroke. When the set point is set to the curve shown by the broken line, when the open angle center timing θ _C is set to the latter half of the intake stroke, it becomes like the curve shown by the solid line, suppressing the torque fluctuation rate and fuel consumption to be low, and improving the exhaust gas property. Can be

In such an internal combustion engine, a recess 4a is provided on the upper surface of the piston 4 facing the combustion chamber 5, and the recess 4a enables the combustion chamber 5 to be made compact. Further, the valve gear 18 is provided with a single camshaft 19 common to both intake valves V _I1 and V _I2 and both exhaust valves V _E1 and V _E2 .
Since the spark plug 45 is arranged in the substantially central portion of the ceiling surface of,
Both intake valves V on the projection view on the plane including the axis of cylinder 3
_The angle formed by the axes of _I1 and V _I2 and the exhaust valves V _E1 and V _E2 can be narrowed, which also enables the combustion chamber 5 to be made compact. By making the combustion chamber 5 compact in this way, the swirl speed generated in the combustion chamber 5 can be increased and the combustibility can be further improved.

Moreover, the lean combustion is executed mainly in the state where the intake valve V _I2 is substantially stopped in the low speed rotation range of the engine, and the fuel injection of the fuel injection valve 55 based on the detection value of the exhaust gas sensor 63 at the time of the lean combustion. By performing feedback control of the amount, lean combustion can be performed while maintaining good combustibility in the combustion chamber 5, and lean combustibility can be improved to reduce fuel consumption. Further, if the injected fuel is atomized by the assist air in the fuel injection valve 55, the lean burnability is further improved.

Further, by slightly opening the intake valve V _I2 to bring it into a substantially resting state, the fuel injected from the fuel injection valve 55 is prevented from staying in the intake port 8 corresponding to the intake valve V _I2 , and the air-fuel ratio It is possible to avoid fluctuations.

By the way, when the operating region of the engine changes from a state mainly in the low speed rotation range to a state mainly in the high speed rotation range, the valve actuation characteristic switching means 35 causes both intake side rocker arms 20, 21 to be in the connection state from the connection release state to the connection state. At the time of switching to, the connection piston 36 of the valve operating characteristic switching means 35 is slightly fitted into the second intake side rocker arm 21, and the first intake side rocker arm 20 is hit by the intake side cam 25, so that The mated state may be lost and the switching may fail.
Thus, when the switching failure occurs during the operation of the intake valve V _{I1 in} the valve opening direction, the second intake side rocker arm 21 moves together with the first intake side rocker arm 20 while swinging in the valve opening direction. 1 The connection with the rocker arm 20 on the intake side is released, and the intake valve V _I2 opens the valve spring 14 during the opening operation.
This causes reversal operation in the valve closing direction, and when the reversal operation in the valve closing direction occurs at a relatively high lift position, the intake valve V _I2 may be impacted and seated on the valve seat.
However, the camshaft 19 is provided with a raised portion 26 corresponding to the second intake-side rocker arm 21, and the raised portion 26 is provided.
Slightly opening angle center timing of the intake valve V _I2 to be opened by theta _C
Is the latter half of the intake stroke, and the valve closing timing θ _VC is set to a timing corresponding to the buffer curve portion A _SC of the lift profile of the intake valve V _I1 by the intake side cam 25. That is, in the intake stroke after the intake valve V _I1 has been lifted to a relatively high position, when the first and second intake side rocker arms 20, 21 are disconnected, the second intake side rocker arm 21 and the intake valve V _I2 The operation will be restricted by the ridge 26. Therefore, even if the intake valve V _I2 reverses in the valve closing direction from the relatively high lift position due to the failure of the valve operating characteristic switching means 35 to switch from the low speed rotation range to the high speed rotation range, the second intake side rocker arm 21 will not move. By restricting the operation in the valve closing direction by the raised portion 26, it is possible to prevent the intake valve V _I2 from being seated by impact, and it is possible to prevent the generation of impact noise.

Further, when the engine is mainly in the low speed rotation range, the valve operating characteristic switching means 35 is switched by the control means 67 to a state where the connection between the intake side rocker arms 20 and 21 is released. Thus, one V _I2 of the intake valves V _I1, V _I2 is substantially become dormant, only the other intake valve V _I1 is made to opened and closed with a timing and a lift amount determined by the intake cam 25.

9 and 10 show a modified example of the valve operating device, and the portions corresponding to the above-mentioned embodiment are designated by the same reference numerals.

This valve operating device 18 'includes a camshaft 19' and first, second and third intake-side rocker arms for converting rotational movement of the camshaft 19 'into opening / closing movements of both intake valves V _I1 , V _I2.
71, 72, 73 and first and second for converting the rotational movement of the camshaft 19 'into the opening / closing movement of the exhaust valves V _E1 and V _E2 .
Exhaust side rocker arms 22 and 23 are provided.

On the camshaft 19 ', a first intake-side cam 74 having a shape corresponding to low-speed operation of the engine and a first intake-side cam 74 formed adjacent to one side of the first intake-side cam 74 while having a shape corresponding to high-speed operation of the engine The second intake cam 75 and the raised portion 76 adjacent to one side of the second intake cam 75 are integrally provided, and
Exhaust side cams 27, 27 on both sides of intake side cam 74 and ridge 76
Are provided integrally.

The one of the intake valves V _I1 interlocked first intake-side rocker arm 71, is connected, the third intake-side rocker arm 73 is linked, is coupled to the other intake valve V _I2, with respect to the intake valves V _I1, V _I2 A second intake-side rocker arm 72, which can be free, is arranged between the first and third intake-side rocker arms 71, 73. Thus, the intake-side rocker arms 71 to 73 are the intake-side rocker shafts 28.
It is rockably supported by. In addition, the first and second exhaust side rocker arms that are individually linked and connected to both exhaust valves V _E1 and V _E2
22 and 23 are swingably supported on the exhaust side rocker shaft 29.

One end of the first intake side rocker arm 71 has a first intake side cam 74.
Slidably in contact with the third intake side rocker arm 73.
The second intake side rocker arm 72 is slidably contacted with the second air supply side cam 75. Also, both exhaust side rocker arms 22, 23
One end of each is slidably contacted with the exhaust side cams 27, 27.

By the way, a support plate 78 is fixedly provided on the upper end of the holder 24, and the support plate 78 is elastically moved in a direction in which the second intake side rocker arm 72 is slidably contacted with the second intake side cam 75 of the cam shaft 19 '. A lost motion mechanism 79 for urging and urging is arranged.

Each intake side rocker arm 71-73 has a valve operating characteristic switching means.
35 'is provided, and this valve operating characteristic switching means 35' is provided.
Is a connecting piston 82 capable of connecting the first intake side rocker arm 71 and the second intake side rocker arm 72, a connecting pin 83 capable of connecting the second intake side rocker arm 72 and the third intake side rocker arm 73, a connecting pin 82, A restricting member 84 that restricts the movement of the connecting pin 83, the connecting piston 82, and the connecting pin 83
And a return spring 85 for urging the regulating member 84 toward the connection release side.

The connecting piston 82 is slidably fitted to the first intake-side rocker arm 71 so as to be movable in the axial direction parallel to the intake-side rocker shaft 28, and is disposed between one end of the connecting piston 82 and the first intake-side rocker arm 71. On the intake side rocker shaft
A hydraulic chamber 86 communicating with the oil passage 41 in 28 is defined. A connecting pin 83, one end of which abuts against the other end of the connecting piston 82, is fitted to the second intake-side rocker arm 72 so as to be slidable in the axial direction parallel to the intake-side rocker shaft 28. Further, a cylindrical bottomed cylindrical regulating member 84 that abuts the other end of the connecting pin 83 is fitted to the third intake side rocker arm 73 so as to be slidable in the axial direction parallel to the intake side rocker shaft 28, and then returned. Spring 85
Is contracted between the restricting member 84 and the third intake-side rocker arm 73.

In the valve operating characteristic switching means 35 ', when the hydraulic pressure in the hydraulic chamber 86 is released mainly in the low speed rotation range of the engine, the return spring 85
Due to the spring force of the connecting piston 82 and the connecting pin 83, the contact surfaces of the connecting pin 82 and the regulating member 84 are in contact with each other between the first intake side rocker arm 71 and the second intake side rocker arm 72. It is located at a position corresponding to between the second intake-side rocker arm 72 and the third intake-side rocker arm 73. Therefore, the rocker arms 71 to 73 are in a state of being capable of relative angular displacement with respect to each other, and the first rotation of the camshaft 19 'causes
The intake-side rocker arm 71 swings in response to the sliding contact with the first intake-side cam 74, and one intake valve V _I1 opens and closes at the timing and lift amount corresponding to the shape of the first intake-side cam 74.
Further, the third intake-side rocker arm 73 that is in sliding contact with the raised portion 76 is substantially in a resting state, and the other intake valve V _I2 can be substantially resting. In addition, the second intake side rocker arm
Although 72 swings in accordance with the sliding contact with the second intake side cam 75, the swinging action is performed by the first and third intake side rocker arms 71, 73.
It has no effect on. Further, the exhaust valves V _E1 and V _E2 are opened and closed at the timing and lift amount according to the shape of the exhaust side cams 27, 27.

By the way, when the lift profile of the intake valve V _I1 by the first intake cam 74 is the curve C shown by the broken line in FIG. 3 (a), the lift profile of the intake valve V _I2 by the raised portion 76 is shown in FIG. It is what is shown by the curve B of a), and an intake valve
The opening angle central timing θ _C of V _I2 is set in the latter half of the intake stroke, preferably in the range of 130 to 180 degrees from the intake stroke start TDC. Moreover, the closing timing θ _VC of the intake valve V _I2 that is slightly opened by the raised portion 76 is determined by the first end side cam 74 indicated by the curve C at the end portion along the crank angle in the lift profile of the intake valve V _I1 . It is set in a portion corresponding to the buffer curve portion C _SC .

When a high hydraulic pressure is applied to the hydraulic chamber 86 mainly in the high-speed rotation range of the engine, the connecting piston 82 moves in a direction of increasing the volume of the hydraulic chamber 86 against the spring force of the return spring 85 while pressing the connecting pin 83. When the axes of the connecting piston 82, the connecting pin 83, and the regulating member 84 are aligned with each other, that is, when the intake-side rocker arms 71 to 73 enter the stationary state, the connecting piston 82 is fitted to the second intake-side rocker arm 72. Then, the connecting pin 33 is fitted into the first intake-side rocker arm 73 accordingly, whereby the intake-side rocker arms 71 to 73 are brought into a connected state. Therefore, the second sliding contact with the second intake side cam 75
The first and third intake-side rocker arms 71 and 73 swing together with the intake-side rocker arm 72, and both intake valves V _I1 and V _I2 are opened and closed at the timing and lift amount according to the shape of the second intake-side cam 75. . Also, both exhaust side rocker arms 22,2
3 opens and closes both exhaust valves V _E1 and V _E2 at a timing and a lift amount according to the shape of the exhaust side cams 27, 27 as in the low speed operation range.

Even in an internal combustion engine equipped with such a valve operating device 18 ', the same effects as those of the above-described embodiment can be obtained by performing the same control as that of the embodiment shown in FIGS.

C. Effect of the Invention As described above, according to the invention of claim, by terminating the fuel injection by the fuel injection valve when one of the intake valves is in the substantially idle state during the intake stroke, The injected fuel can be sequentially introduced into the combustion chamber internal combustion engine in the state where the other intake valve is open to achieve axial stratified charge to improve combustibility.

According to the invention as set forth in claim 1, the fuel injected from the fuel injection valve when one of the intake valves is substantially in the rest state is sequentially introduced into the combustion chamber in the state where the other intake valve is open to axially move the fuel. Achieving stratified charge, increasing the swirl speed associated with the formation of a compact combustion chamber by providing a recess in the top surface of the piston, and the opening angle central timing of one intake valve in the substantially resting state In the latter half, the combustibility can be further improved by suppressing the occurrence of swirl turbulence, and the torque fluctuation can be suppressed by setting the fuel injection end timing in the first half of the intake stroke.

Further, according to the invention as set forth in claim 1, the fuel injected from the fuel injection valve when one of the intake valves is substantially in the rest state is sequentially introduced into the combustion chamber with the other intake valve opened to axially Achieving stratified charge, a single common camshaft for both intake and exhaust valves, and an upper surface of the piston facing the combustion chamber with an ignition plug in the center of the ceiling. The swirl velocity is increased due to the formation of a compact combustion chamber due to the formation of the recessed portion, and the swirl turbulence is suppressed by setting the opening angle central timing of the one intake valve in the substantially idle state as the latter half of the intake stroke. Thus, the combustibility can be further improved, and the torque fluctuation can be suppressed because the fuel injection end timing is in the first half of the intake stroke.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram, FIG. 2 is an enlarged plan view of a partial cutout taken along line II-II of FIG. FIG. 3 is a diagram showing a relationship between an intake valve operating state and fuel injection timing, FIG. 4 is a flow chart showing a procedure for executing feedback control, and FIG. 5 is an experimental result of influence of fuel injection timing on combustion stability. FIG. 6 is a graph showing the experimental results of the influence of the fuel injection end timing on the torque fluctuation rate, and FIG. 7 is an experiment of the influence on the combustion limit by the opening angle central timing of the intake valve in the substantially idle state. Fig. 8 is a graph showing the results, Fig. 8 is a graph showing the experimental results of the effects on the torque fluctuation rate, fuel consumption and exhaust gas properties due to the difference in the opening angle center timing of the intake valve in the substantially resting state, Figs. 9 and 10 are FIG. 9 shows a modified example of the valve operating device, and FIG. Vertical sectional side view taken along the line IX-IX of Figure 10, FIG. 10 is a sectional view taken along line X-X of Figure 9. 4 ... Piston, 4a ... Recessed part, 5 ... Combustion chamber, 8 ... Intake port, 18,18 '... Valve operating device, 19,19' ... Camshaft, 45 ...
Spark plug, 55 ... Fuel injection valve, 61 ... Exhaust pipe, 63 ... Exhaust gas sensor, 67 ... Control means, V _E1 , V _E2 ... Exhaust valve, V _I1 , V _I2 ...
Intake valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI technical display location F02D 41/34 F 9247-3G (72) Inventor Takatoshi Aoki 1-4-1 Wako-Chu, Wako-shi, Saitama (56) Reference JP 62-32205 (JP, A) JP 63-124817 (JP, A) JP 62-288305 (JP, A) JP 64 -80735 (JP, A) JP 61-261639 (JP, A) JP 62-288333 (JP, A) Actually opened 60-195913 (JP, U) Actually opened 63-14828 (JP, U) )

Claims (7)

[Claims] 1. A pair of intake valves (V _I1) configured to open one intake valve (V _I2 ) by a very small amount that is substantially in a rest state during an intake stroke in a low speed operation range of an engine. , V _I2 ), and fuel can be evenly injected toward a pair of intake ports (8) individually corresponding to both intake valves (V _I1 , V _I2 ) Fuel injection valve (5
5) and a control means (67) for controlling the operation of the fuel injection valve (55), the control means (67)
Is configured to control the fuel injection valve (55) by setting the fuel injection end timing during the intake stroke when one of the intake valves (V _I1 , V _I2 ) (V _I2 ) is in the substantially idle state. Internal combustion engine characterized by. 2. The center angle of opening of only one of the intake valves (V _I1 , V _I2 ) (V _I2 ) is set in the latter half of the intake stroke. Internal combustion engine. 3. The internal combustion engine according to claim 1, wherein the fuel injection end timing is set in the first half of the intake stroke. 4. A pair of intake valves (V _I1) configured to open one intake valve (V _I2 ) by a very small amount that is substantially in a rest state during an intake stroke in a low speed operation range of an engine. , V _I2 ), and fuel can be evenly injected toward a pair of intake ports (8) individually corresponding to both intake valves (V _I1 , V _I2 ) Fuel injection valve (5
5) and a control means (67) for controlling the operation of the fuel injection valve (55), and at least the one intake valve (V _I2 )
A combustion chamber (5) of a piston (4) in an internal combustion engine capable of lean combustion in an engine operating range where
The surface facing the recess (4) forming part of the combustion chamber (5)
a) is provided, and the valve operating device (18, 18 ′) is configured such that the center angle of opening of one intake valve (V _I2 ) in a substantially resting state is in the latter half of the intake stroke. 67) is configured to control the fuel injection valve (55) by setting the fuel injection end timing in the first half of the intake stroke when the one intake valve (V _I2 ) is in a substantially _idle state. Internal combustion engine. 5. The valve operating device (18 ') substantially _keeps one intake valve (V _I2 ) in a resting state and the other intake valve (V _I1 ) mainly for a low speed operation range of the engine. Opening / closing operation in the opening / closing operation mode and both intake valves (V _I1 , V
The internal combustion engine according to claim 1, characterized in that it can be switched between a state in which _I2 ) is opened and closed together in an opening and closing operation mode mainly corresponding to a high speed operation range of the engine. 6. An exhaust pipe (61) is provided with an exhaust gas sensor (63) capable of linearly detecting an exhaust gas composition, and the exhaust gas sensor (63) is a control means for performing feedback control during lean combustion of the engine. Internal combustion engine according to claim 1, characterized in that it is connected to (67). 7. An intake valve (V _I1 , V _I2 ) and a pair of exhaust valves (V _E1 , V _E2 ), which are connected to a pair of intake valves (V _I1 , V _I2 ) and one intake valve (V _I2 ) A valve train (18,18 ') configured to open a very small amount that makes it virtually idle, and both intake valves (V _I1 , V _I2 ).
A fuel injection valve (55) capable of uniformly injecting fuel toward a pair of intake ports (8) individually corresponding to the above, and a control means (67) for controlling the operation of the fuel injection valve (55). In an internal combustion engine capable of lean combustion in an engine operating region in which at least one of the intake valves (V _I2 ) is in a substantially resting state, combustion in which a spark plug (45) is arranged substantially in the center of the ceiling surface A recess (4a) forming a part of the combustion chamber (5) is provided on the upper surface of the piston (4) facing the chamber (5), and the valve operating device (18, 18 ') includes both intake valves (V). _I1 , V _I2 ) and a single camshaft (19,1) common to both exhaust valves (V _E1 , V _E2 ).
9 '), and one of the intake valves (V _I2 ) is configured such that the center angle of the opening angle of the intake valve (V _I2 ) in the substantially resting state is in the latter half of the intake stroke, and the control means (67) controls the one intake valve (V An internal combustion engine configured to control a fuel injection valve (55) by setting a fuel injection end timing in the first half of an intake stroke when _I2 ) is substantially in a rest state.