JPH0494433A - Internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention A9 Purpose of the Invention (1) Industrial Field of Application The present invention is mainly concerned with the purpose of reducing air intake valves to the extent that one intake valve is substantially at rest during the intake stroke in the low-speed operating range of the engine. a valve operating device connected to a pair of intake valves and configured to open by the same amount, and a fuel injection valve capable of evenly injecting fuel toward a confluence of a pair of intake ports individually corresponding to both intake valves;
The present invention relates to an internal combustion engine including a control means for controlling the operation of the fuel injection valve.

(2) Conventional technology Conventionally, one of a pair of intake valves (intake valve) is lifted by a small amount in a low engine speed operating range to prevent an increase in fuel consumption in the engine low speed operating range and to keep the intake valve in a substantially closed state. An internal combustion engine that avoids fuel accumulation in an intake port to achieve combustion stability is disclosed, for example, in Japanese Utility Model Application Publication No. 195913/1983.

(3) Problems to be Solved by the Invention When one intake valve is put into a substantially inactive state as in the above-mentioned conventional system, the air-fuel mixture essentially flows into the combustion chamber only from the other intake valve side. It is possible to form a swirl within the combustion chamber.

Incidentally, combustibility can be improved by axially stratified air supply in which the fuel concentration is varied along the axial direction within the combustion chamber and a rich zone with relatively high fuel concentration is formed around the spark plug. It has been known in the past, and by combining the swirl formation and the axial stratified air supply, combustibility will be further improved and stable lean combustion will be possible.

However, in an operating state in which one intake valve is substantially at rest, the inventor's experiments have shown that axial stratified air supply is possible only when the fuel injection timing by the fuel injection valve is at a specific timing. It was revealed by

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an internal combustion engine that improves combustibility by making it possible to supply air in an axially stratified manner in an operating state in which one intake valve is substantially at rest.

B0 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the invention as set forth in claim 1, one intake valve is closed mainly during the intake stroke in the low speed operating range of the engine. A valve operating device connected to a pair of intake valves that is configured to open only a minute amount that is considered to be in a substantially idle state, and a valve train that distributes fuel evenly toward a pair of intake ports that individually correspond to both intake valves. In an internal combustion engine comprising an injectable fuel injection valve and a control means for controlling the operation of the fuel injection valve, the control means terminates fuel injection during an intake stroke when one of both intake valves is substantially at rest. The fuel injection valve is configured to control the fuel injection valve at a determined time.

Further, according to the invention described in claim 1, the pair of intake valves is configured to open only a small amount to the extent that one of the intake valves is substantially in a rest state during the intake stroke mainly in the low-speed operating range of the engine. A valve operating device connected to the valve, a fuel injection valve capable of evenly 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 with at least one of the intake valves in a substantially idle state, the piston has a recess forming a part of the combustion chamber on a surface 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 rest state is in the latter half of the intake stroke, and the control means is configured such that the opening angle center timing of the one intake valve is in the substantially rest state. In some cases, the fuel injection valve is controlled by determining the fuel injection end timing in the first half of the intake stroke.

Furthermore, according to the invention set forth in claim 1, the intake valves are connected to a pair of left and right intake valves and a pair of exhaust valves, and one of the intake valves is kept in a substantially inactive state during the intake stroke mainly in the low-speed operating range of the engine. A valve train configured to open only a minute amount to the extent that it opens, a fuel injection valve that can evenly inject fuel toward a pair of intake ports individually corresponding to both intake valves, and a fuel injection valve that controls the operation of the fuel injection valve. an internal combustion engine capable of lean combustion in an engine operating range with at least one of the intake valves in a substantially idle state, the combustion engine having a spark plug disposed substantially in the center of the ceiling surface; The upper surface of the piston facing the chamber is provided with a recess that forms part of the combustion chamber, and the valve train has a single camshaft that is common to both intake valves and both exhaust valves, and a single camshaft that is common to both intake valves and both exhaust valves. The central timing of color opening in the substantially resting state is configured to be in the latter half of the intake stroke, and the control means determines the fuel injection end timing in the first half of the intake stroke when the one intake valve is in the substantially resting state. The fuel injection valve is configured to control the fuel injection valve.

(2) Effect According to the structure of the invention described in claim 1, the fuel injection by the fuel injection valve when one of the two intake valves is substantially in a rest state is completed during the intake stroke, so that the fuel injection It is possible to sequentially introduce the injected fuel from one valve into the combustion chamber with the other intake valve open to achieve axially stratified air supply.

Further, according to the configuration of the invention described in claim 1, when one of the two intake valves is substantially in a rest state, the injected fuel from the fuel injection valve is sequentially introduced into the combustion chamber while the other intake valve is in the open state. It is possible to achieve stratified air supply in the axial direction, and it is also possible to promote improvement in combustibility by increasing the swirl speed due to the formation of a compact combustion chamber by providing a recess on the top surface of the piston. By setting the fuel injection end timing in the first half of the intake stroke, torque fluctuations can be suppressed, and by setting the opening angle center timing of one intake valve in the substantially resting state to the second half of the intake stroke, one intake valve It is possible to suppress the occurrence of swirl disturbance caused by the slight opening of the valve.

Furthermore, according to the structure of the invention described in claim 2 above, when one of the two intake valves is substantially in a rest state, the injected fuel from the fuel injection valve is sequentially introduced into the combustion chamber with the other intake valve in the open state. In addition, a single common camshaft is provided for both intake valves and both exhaust valves, and the spark plug is located approximately in the center of the ceiling surface. By providing a recess on the top surface of the piston facing the combustion chamber, it is possible to form a more compact combustion chamber, and by making the combustion chamber more compact, it is possible to promote improved combustibility by increasing the swirl speed. Furthermore, by setting the fuel injection end timing in the first half of the intake stroke, torque fluctuations can be suppressed, and by setting the opening angle center timing of one intake valve in the substantially resting state to the second half of the intake stroke, it is possible to suppress torque fluctuations. It is possible to suppress the occurrence of swirl disturbances caused by the slight opening of the intake valve.

(3) Examples Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 8 show an embodiment of the present invention,
Fig. 1 is an overall configuration diagram, Fig. 2 is a partially cutaway enlarged plan view along the line ■-■ in Fig. 1, Fig. 3 is a diagram showing the relationship between the intake valve operating state and fuel injection timing, and Fig. Figure 5 is a flowchart showing the procedure for executing feedback control, Figure 5 is a graph showing the experimental results of the effect of fuel injection timing on combustion stability, and Figure 6 is a graph showing the effect of fuel injection end timing on torque fluctuation rate. Graph showing the experimental results. Figure 7 is a graph showing the effect of the opening angle center timing of the intake valve in the substantially resting state on the combustion limit. Figure 8 is the opening angle center of the intake valve in the substantially resting state. Torque fluctuation rate due to timing differences,
It is a graph showing the experimental results of the influence on fuel efficiency and exhaust gas properties.

First, in FIG. 1, a cylinder block 1 is constructed to constitute the main part of the engine body in a 5OHC multi-cylinder internal combustion engine.
A cylinder head 2 is coupled to the upper surface, and a plurality of cylinders 3 provided in the cylinder block 1 have recesses 4a on the upper surface.
The pistons 4 having the above pistons 4 are slidably fitted to each other, and combustion chambers 5 are formed between the upper surfaces of the pistons 4 and the cylinder head 2, respectively.

A pair of intake valve ports 6 and a pair of exhaust valve lowers are provided in the cylinder head 2 so as to open at the ceiling surface of the combustion chamber 5. The cylinder head 2 also has a pair of intake ports 8 which are branched from a single intake opening end 9 that opens on the lower side of the cylinder head 2 and which are individually connected to the pair of intake valve ports 6, and a pair of intake ports 8 which are individually connected to the pair of exhaust valve lowers. A pair of exhaust ports 10 are provided which are connected to a single exhaust opening end 11 which is connected to the cylinder head 2 and which is opened to the other side of the cylinder head 2 . A pair of intake valves Vr+ and V□2, which can open and close both intake valve ports 6 individually, are slidably fitted into a pair of guide tubes 12 provided in the cylinder head 2, and each guide tube A coil-shaped valve spring 14 that surrounds each intake valve VXI+V12 is fixed to the upper end of each intake valve V I, VI2 protruding from 12, and between the retainer 13 and the cylinder head 2. The valve springs 14 urge each intake valve V, . Further, a pair of exhaust valves VEI, V, 2, which can open and close both exhaust valve lowers individually, are slidably fitted into a pair of guide tubes 15 disposed in the cylinder head 2, and each guide tube Each exhaust valve V protrudes from 15! l,
Each exhaust valve V E l +
Coiled valve springs 17 surrounding VH2 are interposed, and these valve springs 17 cause each exhaust valve VE,...
V. is urged upward, that is, in the valve closing direction.

Referring also to FIG. 2, a valve train 18 is connected to both intake valves VII+VE2 and both exhaust valves Vt+, VE. This valve train 18 includes a single camshaft 19 that is interlocked and connected to a crankshaft (not shown) at a reduction ratio of 1/2, and a rotational movement of the camshaft 19 that controls both intake valves V11. first and second intake side rocker arms 20.21 for converting the rotational movement of the camshaft 19 into opening and closing movements of both exhaust valves Vゎ+VE2; Exhaust side rocker arms 22 and 23 are provided.

The camshaft 19 includes a cylinder head 2 and holders 24 respectively coupled on the cylinder head 2 on both sides of the cylinder 3 along the axis of the crankshaft 19.
It has a horizontal axis perpendicular to the axis of the cylinder 3 and is rotatably supported.

The camshaft 19 is integrally provided with an intake cam 25 and a protrusion 26 disposed adjacent to one side of the intake cam 25, and an exhaust cam on both sides of the intake cam 25 and the protrusion 26. 27, 27 are provided integrally. The raised portion 26 is mainly used for both intake valves V in the low speed operating range of the engine.
. +, vr2 is basically formed to have a circular outer surface centered on the axis of the camshaft 19 in order to put VI2 into a rest state, but the higher part of the intake side cam 25 A slightly protruding protrusion is provided at a position corresponding to . Moreover, the width of the raised portion 26 in the direction along the axis of the camshaft 19 is set to be relatively narrow.

A first intake side rocker arm 20 is interlocked and connected to one intake valve VX, a second intake side rocker arm 21 is moved and connected to the other intake valve VI2, and both intake side rocker arms 20.21 are connected to the camshaft. The holder 24 has an axis parallel to the camshaft 19 at a position diagonally above the camshaft 19.
It is swingably supported by an intake side rocker shaft 28 which is fixedly supported by the intake rocker shaft 28 . Also, both exhaust side rocker arms 22.2
3 is an exhaust side rocker which is individually interlocked and connected to both exhaust valves V and Vaz, and is fixedly supported by the holder 24 in parallel with the intake side rocker shaft 28 at a position diagonally above the camshaft 19; It is swingably supported by a shaft 29.

An intake cam 25 is provided at one end of the first intake side rocker arm 20.
A roller 30 that comes into sliding contact with the raised portion 26 is rotatably supported, and a sliding contact portion 31 that comes into sliding contact with the raised portion 26 is provided at one end of the second intake-side rocker arm 21 while having a narrow width corresponding to the raised portion 26 . Furthermore, rollers 32 that slide in sliding contact with the exhaust side cams 27.27 are each pivotally supported at one end of both the exhaust side rocker T-arms 22.23.

Tappet screws 33 that come into contact with the upper ends of both intake valves Vi++ VI2 are respectively screwed into the other ends of the first and second intake side rocker arms 20.21 so as to be able to move forward and backward. Each intake valve Vr0. V□ will open and close. In addition, tappet screws 34 that come into contact with the upper ends of each exhaust valve VY++Viz are screwed into the other ends of both exhaust side rocker arms 22 and 23 so that they can move forward and backward.
2. Each exhaust valve V, .

On both intake side rocker arms 20.21, both intake valves V! r
, Vxz operating characteristics mainly in the low speed rotation range of the engine,
A valve operation characteristic switching means 35 is provided which can switch between a connected state of both intake side rocker arms 20.21 and a disconnected state of both intake side rocker arms 20.21 in order to switch mainly in the high speed rotation range of the engine.

This valve operation characteristic switching means 35 includes a connecting piston 36 that can connect both intake-side rocker arms 20.21, a regulating member 37 that restricts movement of the connecting piston 36, and a connecting piston 36 and regulating member 37 that move the connecting piston 36 and the regulating member 37 to the disconnecting side. A biasing return spring 38 is provided.

The connecting piston 36 defines a hydraulic chamber 39 between its one end and the first intake rocker arm 20, and is movable in an axial direction parallel to the intake rocker shaft 28 so as to slide on the first intake rocker arm 2o. possible to be mated. Further, a communication passage 40 communicating with the hydraulic chamber 39 is bored in the first intake rocker arm 20, and the communication passage 40 is provided in the intake rocker shaft 28 regardless of the rocking state of the first intake rocker arm 20. An oil passage 41 (see FIG. 1) is provided that constantly communicates with the hydraulic chamber 39. Therefore, the oil passage 41
is connected to a hydraulic power source 43 via a connection switching electromagnetic control valve 42, as shown in FIG.

The second intake side rocker arm 21 has the connecting piston 3
a bottomed cylindrical regulating member 3 whose closed end is in contact with the other end of 6;
7 is slidably fitted. Further, the return spring 38 is compressed between the second intake-side rocker arm 21 and the regulating member 37, and the spring force of the return spring 38 causes the connecting piston 36 and the regulating member 37 that are in contact with each other to move into the hydraulic chamber 3.
It is biased toward the 9 side.

In this valve operation characteristic switching means 35, the hydraulic pressure in the hydraulic chamber 39 is released by the electromagnetic control valve 42 for connection switching mainly in the low speed operating range of the engine, and the spring force of the return spring 38 causes the connection piston 36 and the regulating member 37 to be released. The abutting surface is located at a position corresponding to between the first and second intake side rocker arms 20,21. Therefore, both intake side rocker arms 2
0 and 21 are in a state where they can be relatively angularly displaced from each other, and the rotation of the camshaft 19 causes the first intake side rocker arm 2 to move.
0 is one intake valve V that swings in response to sliding contact with the intake side cam 25. 1 opens and closes with timing and lift amount depending on the shape of the intake side cam 25.

Also, the second intake side rocker arm 21 is in sliding contact with the raised portion 26.
is substantially at rest, which causes the other intake valve V12 to become substantially at rest. Moreover, the intake valve VI2 does not completely stop, but when one intake valve Vll opens, it moves slightly in the opening direction, so the valve seat of the intake valve VI2 that occurs when the intake valve VI2 is kept in a completely closed state. It is possible to prevent fuel from sticking to the fuel and from stagnation of fuel. Further, the exhaust valve VΣhV is opened and closed at a timing and lift amount depending on the shape of the exhaust side cam 27, 27.

By the way, when the intake valve V construction and slope profile by the intake side cam 25 is as shown by curve A in FIG. 3(a), the intake valve Vf is slightly opened by the raised portion 26.
The lift profile of No. 2 is as shown by curve B in FIG. 3(a), and its opening angle center timing θ. is set in the latter half of the suction stroke when the intake valve VII is open, preferably in the range of 130 to 180 degrees from the suction stroke start TDC.

Moreover, the intake valve VI is slightly opened by the raised portion 26.
The valve closing timing θvc of No. 2 is determined by the intake side cam 2 shown by curve A.
In order to alleviate the impact when the intake valve Vll is seated, the buffer curved part ASCS at the terminal end along the crank angle in the lift profile of the intake valve V□ due to the intake valve Vll is
It is set at a portion corresponding to the operation profile of the intake valve V, + corresponding to the transition portion from the upper part to the inside of the base in No. 5.

Further, the lift amount of the intake valve V12 is set to, for example, about 0.4 to 2.0 degrees.

Mainly when the engine is operating at high speed, the connection switching electromagnetic control valve 42 is opened to apply high oil 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 a rest state, the connecting piston 36 fits into the second intake side rocker arm 21, and both intake side rocker arms 20.
21 are in a connected state, the second intake rocker arm 21 swings together with the first intake rocker arm 20 that is in sliding contact with the intake cam 25, and both intake valves VII+vr2 assume the shape of the intake cam 25. The opening/closing operation is performed at appropriate timing and lift amount (profile shown by curve A in FIG. 3(a)). In addition, both exhaust side rocker arms 22.23 operate both exhaust valves V
Operate opening and closing.

The cylinder head 2 has both exhaust side rocker arms 22.2.
A plug cylindrical portion 44 is provided so as to be inclined laterally as it goes upward between 3 and 3.
A spark plug 45 inserted from the combustion chamber 5 is attached to the cylinder head 2 at a substantially central portion of the ceiling surface of the combustion chamber 5.

Referring again to FIG. 1, the intake opening end 9 of the cylinder head 2
An air cleaner 49 is connected via an intake manifold 46 and a throttle body 48 having a throttle valve 47.
is connected. 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.
, a bypass passage 51 and a fast idle passage 5 are provided.
2 are connected in parallel bypassing the throttle valve 47, a bypass electromagnetic control valve 53 is interposed in the bypass passage 51, and a wax valve that operates according to the cooling water temperature of the engine body is provided in the first idle passage 52. A valve 54 is interposed.

A fuel injection valve 55 is attached to the end of the intake manifold 46 on the side of the cylinder rad 2 in order to inject fuel evenly from the intake opening end 9 toward both intake ports 8. A supply 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 to atomize the injected fuel. A passage 57 for supplying assist air is connected to the fuel injection valve 55. The passage 57 is connected to an air header 58 common to each cylinder. It is connected to the intake passage 50 on the side.

A catalytic converter 62 is connected to the exhaust opening end 11 of the cylinder head 2 via an exhaust manifold 61.
An exhaust gas sensor 63 that can linearly detect the 02 concentration in exhaust gas is attached to the exhaust manifold 61.

The operation of the connection switching electromagnetic control valve 42, the bypass electromagnetic control valve 53, the fuel injection valve 55, and the electromagnetic air amount control valve 59 is controlled by a control means 67 consisting of a computer. Intake pressure sensor 6
The intake pressure P B % detected at 4, the cooling water temperature Tw detected by the cooling water temperature sensor 65, and the engine rotation speed N6 detected by the rotation speed sensor 66 are input, and feedback during lean combustion of the engine is input. The detected value of the exhaust gas sensor 63 is input for control.

Thus, the control means 67 controls both intake valves V! when the engine is mainly in a low speed rotation range. l+ V One of 12 VX
Both intake side rocker arms 20
．． 21 is in a disconnected state, and when the engine is mainly in a high speed range, the valve operation characteristics are switched so that both intake rocker arms 20 and 21 are in a connected state so that both intake valves VII+VI2 are opened and closed by the intake cam 25. In addition to controlling the operation of the means 35, when the engine is mainly in a low speed rotation range, that is, when one of the intake valves V, I and V is substantially at rest, the fuel injection valve 55 injects fuel. As shown in Fig. 3, etc., the fuel injection end timing θFE is during the intake stroke, and is preferably in the first half of the intake stroke, for example, at 5 pm from the start of the intake stroke TDC.
The angle is controlled to be within the range of 0 to 90 degrees.

Further, the control means 67 controls the amount of fuel injected from the fuel injection valve 55 to achieve lean combustion when the engine is mainly in a low speed rotation range, and during lean combustion, the exhaust gas sensor Feedback control of the fuel injection amount is performed based on the detected value of 63.

In FIG. 4, in the first step S1, the exhaust gas sensor 6
The detected value No. 3 is read, and in a second step S2 it is determined whether the engine is in a starting state. In the engine starting state, the process proceeds from the second step S2 to the third step S3.
In this third step S3, the correction coefficient K LAP used in calculating the fuel injection amount, which will be described later, is r1. After setting the target air-fuel ratio to the engine starting air-fuel ratio in the next 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 T1 of the fuel injection valve 55 is the following (1)
It is carried out based on the formula.

Tx=T4×KoolIXKLAFXKX+C...(
1) In this equation (1), TIM is the engine speed NI
Kcxnx is a basic injection time preset based on engine speed N6 and intake pressure Pi, and Kcxnx is a correction coefficient for correcting the target air-fuel ratio by intake air amount, which is preset based on engine speed N6 and intake pressure Pi. So, basically (T
+i+X K CIIDK), the injection time for the target air-fuel ratio is determined. Further, K LAF is a correction coefficient for feedback control according to the detected value of the exhaust gas sensor 63, and r 1. During OJ, feedback control is not executed. Further, 1 is a correction coefficient based on water temperature, atmospheric pressure, etc., and C is a correction coefficient based on battery voltage, vehicle acceleration, etc. that affect the fuel injection operation of the fuel injection valve 55.

In the sixth step S6, the fuel injection time timing is calculated so that the fuel injection end timing θ is within the intake stroke, preferably in the first half of the intake stroke, taking into account the engine speed Nll, and in the next seventh step S7. The fuel injection time T, 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 second step S2
The program then proceeds to an eighth step S8, in which a target air-fuel ratio is calculated using a preset map based on the engine speed Ny and the intake pressure Pil. Then, in the next ninth step S9, the exhaust gas sensor 63
It is determined whether or not it is in an active state. This is to judge whether the exhaust gas sensor 63 is in a state where it can perform a normal detection function, for example, based on the temperature of the exhaust gas sensor 63. If it is determined that it is not in an active state, a correction coefficient is set in a tenth step S10. K LAF is r 1
．． After being set to OJ, the process proceeds to the fifth step S5, and when it is determined that it is in the active state, the process proceeds to the eleventh step S1.
Proceed to l.

In the eleventh step Sll, the actual air-fuel ratio is calculated based on the detected value of the exhaust gas sensor 63. In other words, the exhaust gas sensor 63 linearly outputs a voltage corresponding to o and m degrees in the exhaust gas, and the actual air-fuel ratio is calculated based on a table set in advance in accordance with the voltage. .

In the twelfth step SL2, it is determined whether feedback control is possible. That is, when a fuel cut is being executed by engine speed control, vehicle speed control, traction control, etc., and immediately after the fuel cut is executed, feedback control based on the detected value of the exhaust gas sensor 63 is executed. It is meaningless, and when the engine cooling water temperature T is extremely low, the injected fuel is not sufficiently atomized and fuel tends to adhere to the inner surface of the intake port 8, so it is obtained based on the detected value of the exhaust gas sensor 63. The actual air-fuel ratio indicates a low fuel concentration, and if feedback control is executed in such a state, the fuel concentration will become unnecessarily high. Therefore, when a fuel cut is being executed, immediately after the fuel cut is executed, and when the engine cooling water temperature T is extremely low, feedback control is prohibited and the twelfth step S is performed.
12, the process proceeds to the tenth step SIO, and in other cases, the process proceeds from the twelfth step SL2 to the thirteenth step S13 assuming that feedback control is to be executed.

In the thirteenth step S13, a correction coefficient K_LAP is calculated based on the difference between the target air-fuel ratio and the actual air-fuel ratio, and the next first
In the fourth step S14, it is determined whether the calculated correction coefficient KLAF is within a certain range, and if it exceeds the range, a predetermined maximum or minimum value is output as the correction coefficient KLAF, and the fifth The process proceeds to step S5, where the fuel injection amount is calculated.

Next, the operation of this embodiment will be explained. When the engine is mainly in a high speed rotation range, the control means 67 controls the valve operating characteristic switching means 35 to control both the intake side rocker arms 20.2.
1 is in a connected state, and the valve train 18 is connected to both intake valves I+V.
The I2 is opened and closed at the timing and lift amount determined by the intake side cam 25.

Further, when the engine is mainly in a low speed rotation range, the control means 67 causes the valve operation characteristic switching means 35 to switch to a state in which the connection between the two intake side rocker arms 20, 21 is released. As a result, one of the two intake valves V, +, V□2 v0. is substantially in a rest state, and only the other intake valve Vll is opened and closed at the timing and lift amount determined by the intake side cam 25.

As a result, the air-fuel mixture substantially flows into the combustion chamber 5 from only one of the intake valve ports 6, and a swirl is formed within the combustion chamber 5. Furthermore, the fuel injection by the fuel injection valve 55 during the swirl generation is controlled so as to end during the intake stroke, and the injected fuel flows from the intake valve port 6 corresponding to the intake valve vr+ which is opening and closing into the combustion chamber. It becomes possible to achieve axially stratified supply air by sequentially introducing the fuel into the fuel cell 5, thereby making it possible to improve the combustibility as shown in FIG. 5, which shows the experimental results of the present inventor.

Further, the fuel injection end timing θ□ by the fuel injection valve 55 is the third
As shown in Figure 6), the first half of the suction stroke is preferably set in the range of 50 to 90 degrees from the suction stroke start TDC. As a result, the torque fluctuation rate can be kept small.

Furthermore, the intake valve V1 is opened slightly by the raised portion 26.
2, opening angle center timing θ. As shown by curve B in Fig. 3(a), 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. It becomes possible to suppress the occurrence of swirl disturbance caused by a slight opening of V12. Therefore, the opening angle center time θ. Figure 7 shows the experimental results of the flammability limit for the opening angle center timing θ. It is clear that the lean burn limit is improved by setting TDC at the latter half of the suction stroke, preferably in the range of 130 to 180 degrees from the suction stroke start TDC. Also, the opening angle center timing θ. Figure 8 shows the results of experiments conducted by the present inventor regarding the effects of differences in torque on torque fluctuations and fuel consumption.
The opening angle center timing θ. When set at the center of the suction stroke, the broken line indicates the opening angle center timing θ. When set in the latter half of the intake stroke, the curve becomes as shown by the solid line, and the torque fluctuation rate and fuel consumption can be kept low, and the exhaust gas properties can be improved.

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 allows the combustion chamber 5 to be made more compact. Also, the valve train 1
8 is both intake valves V flu VI2 and both exhaust valves VE1
．． It is equipped with a single camshaft 19 that is common to V It is possible to narrow the angle formed by the axes of both intake valves VTII V+2 and both exhaust valves Via and VB2 on the projection view, and this also allows the combustion chamber 5 to be made more compact. By making the combustion chamber 5 more compact as described above, it is possible to increase the swirl velocity generated within the combustion chamber 5 and further improve the combustibility.

Moreover, lean combustion is performed mainly in the low speed rotation range of the engine when the intake valve VI2 is substantially stopped, and during this lean combustion, the fuel injection amount of the fuel injection valve 55 is determined based on the detected value of the exhaust gas sensor 63. By performing feedback control, it is possible to perform lean combustion while maintaining good combustibility within the combustion chamber 5, and it is possible to improve lean burnability and reduce fuel consumption. Furthermore, fuel injection valve 5
When the injected fuel is atomized by the assist near operation in step 5, lean burnability is further improved.

Intake valve V again! 2 is slightly opened to bring it into a substantially idle state, thereby preventing the fuel injected from the fuel injection valve 55 from remaining in the intake boat 8 corresponding to the intake valve VI2, causing fluctuations in the air-fuel ratio. It is possible to avoid this.

By the way, when the operating range 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 operation characteristic switching means 35 changes the two intake side rocker arms 20 and 21 from the disconnected state to the connected state. When switching to the first intake side rocker arm 20 by the intake side cam 25, with the connecting piston 36 of the valve operating characteristic switching means 35 slightly fitted into the second intake side rocker arm 21.
If the connector is hit, the fitted state may come off and the switching may fail. Therefore, when the switching failure occurs during the operation of the intake valve vr+ in the valve opening direction, the second intake side rocker arm 21 and the first intake side rocker arm 20 move together with the first intake side rocker arm 20 while the first intake side rocker arm 21 is swinging in the valve opening direction. Intake side Rotsuka arm 2
0 is released, the intake valve VX2 is reversely operated in the valve-closing direction by the valve spring 14 during the valve-opening operation, and the reversal operation in the valve-closing direction is at a relatively high lift position. When this occurs, there is a risk that the intake valve V1□ may be impulsively seated on the valve seat. However, the camshaft 19 has a raised portion 2 corresponding to the second intake side rocker T-arm 21.
6 is provided, and the concave angle center timing θ of the intake valve VI2 is slightly opened by the raised portion 26. is the latter half of the intake stroke, and the valve closing timing θvc is the intake side cam 25.
Buffer curve part As of the lift profile of intake valve V
It is set at the time corresponding to c. That is, the intake valve V
During the intake stroke after l+ has been lifted to a relatively high position, when the first and second intake side rocker arms 20.21 are disconnected, the operation of the second intake side rocker arm 21 and the intake valve valve mechanism is raised. It will be regulated by Section 26. Therefore, even if the intake valve V□ is reversely operated in the valve closing direction from a relatively high lift position due to a failure in switching from a low speed rotation range to a high speed rotation range by the valve operation characteristic switching means 35, the second
By restricting the operation of the intake-side rocker arm 21 in the valve-closing direction by the raised portion 26, the intake valve V□ is prevented from being seated in a balanced manner, and the generation of impact noise can be prevented.

Further, when the engine is mainly in a low speed rotation range, the control means 67 causes the valve operation characteristic switching means 35 to switch to a state in which the connection between the two intake side rocker arms 20, 21 is released. As a result, one of the two intake valves V, .

9 and 10 show a modification of the valve train, and parts corresponding to those in the above-described embodiment are given the same reference numerals.

This valve train 18' includes a camshaft 19' and first, second, and third intake side rocker arms 71 for converting the rotational movement of the camshaft 19' into opening/closing movement of both intake valves V□1°VI2. .72.73 and the camshaft 19
first and second exhaust side rocker arms 22 for converting the rotational movement of ″ into the opening/closing movement of both exhaust valves V11+V12.
．． 23.

The camshaft 19' includes a first intake cam 74 having a shape suitable for low speed operation of the engine, and a first intake cam 74 formed in a shape suitable for high speed operation of the engine and arranged adjacent to one side of the first intake cam 74. Second intake side cam 75 and second intake side cam 75
A raised portion 76 adjacent to one side of the first intake cam 74 is integrally provided, and exhaust side cams 27, 27 are integrally provided on both sides of the first intake side cam 74 and the raised portion 76.

A first intake side rocker arm 71 is interlocked and connected to one intake valve V□1, a third intake side rocker arm 73 is interlocked and connected to the other intake valve VZ2, and both intake valves Vll,
A second intake rocker arm 72, which can be free with respect to Vf2, is arranged between the first and third intake rocker arms 71,73. Therefore, each intake side rocker arm 71 to 73
is swingably supported by the intake side rocker shaft 28.

Further, first and second exhaust side rocker arms 22, 23, which are individually interlocked and connected to both exhaust valves VEI and Vi□, are swingably supported by an exhaust side rocker shaft 29.

One end of the first intake side rocker arm 71 is connected to the first intake side cam 7.
One end of the third intake-side rocker arm 73 is in sliding contact with the raised portion 76, and the second intake-side rocker arm 72 is in sliding contact with the second @, air-side cam 75. Further, one ends of both exhaust side rocker arms 22, 23 are in sliding contact with exhaust side cams 27, 27, respectively.

By the way, a support plate 78 is fixed to the upper end of the holder 24, and this support plate 78 has a resilient force in the direction of sliding the second intake side rocker arm 72 into sliding contact with the second intake side cam 75 of the camshaft 19'. A lost motion mechanism 79 for energizing is provided.

Each intake-side rocker arm 71 to 73 is provided with a valve operating characteristic switching means 35'.
5' is a connection piston 82 that can connect the first intake side rocker arm 71 and the second intake side rocker arm 72, and a connection that can connect the second intake side rocker T-arm 72 and the third rgL air side rocker T-arm 73. A regulating member 84 that regulates the movement of the pin 83 and the connecting piston 82 and the connecting pin 83.
, the connecting piston 82 , the connecting pin 83 and the regulating member 8
4 toward the disconnection side.

The connecting piston 82 is movable in an axial direction parallel to the intake rocker shaft 28 and is connected to the first intake rocker arm 7 .
A hydraulic chamber 86 communicating with the oil passage 41 in the intake rocker shaft 28 is defined between one end of the connecting piston 82 and the first intake rocker arm 71 . A connecting pin 83 whose one end abuts the other end of the connecting piston 82 is fitted into the second intake rocker arm 72 so as to be slidable in an axial direction parallel to the intake rocker shaft 28 . Even the third one! The air side rocker arm 73 has a bottomed cylindrical regulating member 84 that comes into contact with the other end of the connecting pin 83.
is fitted to be slidable in an axial direction parallel to the intake rocker shaft 28, and the return spring 85 is compressed between the regulating member 84 and the third intake rocker arm 73.

In this 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 spring force of the return spring 85 causes the contact surfaces of the connecting piston 82 and the connecting pin 83 to change to the first @, It is located at a position corresponding to between the air side rocker arm 71 and the second intake side rocker arm 72, and the contact surfaces of the connecting pin 83 and the regulating member 84 are between the second intake side rocker arm 72 and the third r! It is located at a position corresponding to between the IiL air side rocker arms 73. Therefore, the rocker arms 71 to 73 are in a state where they can be angularly displaced relative to each other, and the first intake-side rocker arm 71 swings in response to sliding contact with the first intake-side cam 74 due to the rotational operation of the camshaft 19''. One intake valve V++ opens and closes with timing and lift amount depending on the shape of the first intake cam 74. Also, the third intake rocker arm 73 in sliding contact with the protrusion 76 is substantially at rest, and the other The intake valve V12 can be stopped in a harmful manner.Furthermore, the second intake-side rocker arm 72 swings in response to sliding contact with the second intake-side cam 75, but the swinging motion is similar to that of the first and third rocker arms 72. Intake side rocker arm 7
1.73 has no effect. Also exhaust valve V *
r+V*2 opens and closes at a timing and lift amount depending on the shape of the exhaust side cam 27.27.

By the way, the 1st rII! Intake valve by L air side cam 74■
When the lift profile of the intake valve V11 is the curve C shown by the broken line in FIG. The opening angle center timing θC of the valve VZ2 is in the latter half of the suction stroke, preferably 1 from the suction stroke start TDC.
It is set in the range of 30 to 180 degrees. In addition, the closing timing θvc of the intake valve V, which is slightly opened by the raised portion 76, is determined by the buffering of the terminal end along the crank angle in the lift profile of the intake valve vr+ by the first intake side cam 74 shown by the curve C. This is set at a portion corresponding to the curved portion CSe.

When high oil 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 to increase 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, connecting pin 83, and regulating member 84 coincide,
That is, when each of the intake side rocker arms 71 to 73 enters a stationary state, the connecting piston 82 fits into the second intake side rocker arm 72, and the connecting pin 33 fits into the second intake side rocker arm 73 accordingly. Each of the intake side rocker arms 71 to 73 is in a connected state. Therefore, the second
The second intake locking arm 72 that is in sliding contact with the intake cam 75 and the first and third intake side opening hook arms 71.
73 swings, and both intake valves V, . Also, both exhaust side rocker arms 22, 2
3, both exhaust valves V are operated at timing and lift amount according to the shape of the exhaust side cam 27.
Open/close V□2.

Even in an internal combustion engine equipped with such a valve operating device 18', effects similar to those of the above-mentioned embodiments can be achieved by performing the same control as the embodiments shown in FIGS. 1 to 8.

Effects of the C0 Invention As described above, according to the invention described in claim 1, by terminating the fuel injection by the fuel injection valve during the intake stroke when one of the two intake valves is in a substantially inactive state, By sequentially introducing the injected fuel into the combustion chamber with the other intake valve open, axially stratified air supply can be achieved, and combustibility can be improved.

Further, according to the invention described in claim 1, when one of the two intake valves is in a substantially inactive state, the injected fuel from the fuel injection valve is sequentially introduced into the combustion chamber with the other intake valve in the open state. Achieving directional stratified air supply, increasing the swirl velocity due to the formation of a compact combustion chamber by providing a recess on the top surface of the piston, and adjusting the opening angle center timing during the intake stroke when one intake valve is substantially at rest. Combustibility can be further improved by suppressing the occurrence of swirl disturbances in the latter half of the intake stroke, and torque fluctuations can be suppressed by setting the fuel injection end timing in the first half of the intake stroke.

Furthermore, according to the invention set forth in claim 1, when one of the two intake valves is in a substantially idle state, the injected fuel from the fuel injection valve is sequentially introduced into the combustion chamber with the other intake valve in the open state. To achieve directional stratified air supply, a single camshaft common to both intake valves and both exhaust valves is provided, and the top surface of the piston faces the combustion chamber with a spark plug located approximately in the center of the ceiling surface. The swirl speed increases due to the formation of a compact combustion chamber by providing a recess in the intake valve, and the opening angle center timing when one intake valve is substantially at rest is set in the latter half of the intake stroke to suppress the occurrence of swirl disturbances. As a result, combustibility can be further improved, and since the fuel injection end timing is in the first half of the intake stroke, torque fluctuations can be suppressed.

[Brief explanation of the drawing]

1 to 8 show one embodiment of the present invention, in which FIG. 1 is an overall configuration diagram, FIG. 2 is a partially cutaway enlarged plan view taken along the line ■-■ in FIG. Figure 3 is a diagram showing the relationship between the intake valve operating state and fuel injection timing, Figure 4 is a flowchart showing the procedure for executing feedback control, and Figure 5 is the experimental result of the influence of fuel injection timing on combustion stability. Figure 6 is a graph showing the experimental results of the influence of the fuel injection end timing on the torque fluctuation rate, Figure 7 is an experiment of the influence of the central opening angle timing of the intake valve in the substantially resting state on the combustion limit. Graphs showing the results, Figure 8 are graphs showing the experimental results of the effects on torque fluctuation rate, fuel consumption and exhaust gas properties due to differences in the opening angle center timing of the intake valve in the substantially rest state, Figures 9 and 10 are 9 is a longitudinal sectional side view taken along line IX-IX in FIG. 10, and FIG. 0 is a sectional view taken along line X-XM in FIG. 9. 4... Piston, 4a... Recess, 5... Combustion chamber,
8...Intake port, 18.18''...Valve train, 1
9.19'...Camshaft, 45...Spark plug, 55...Fuel injection valve, 61...Exhaust pipe, 63...
・Exhaust gas sensor, 67...control means,

Claims (7)

[Claims] (1) The pair of intake valves (V_I_2) are configured to open only a small amount to the extent that one intake valve (V_I_2) is substantially stopped during the intake stroke mainly in the low-speed operating range of the engine.
I_1, V_I_2) connected to the valve train (18, 1
8′), a fuel injection valve (55) capable of evenly injecting fuel toward a pair of intake ports (8) that individually correspond to both intake valves (V_I_1, V_I_2);
5), the control means (67) controls the operation of both intake valves (V_I
_2, V_I_2) is in a substantially inactive state, the internal combustion engine is configured to determine the end timing of fuel injection during the intake stroke and control the fuel injection valve (55). (2) One (V_I_1, V_I_2) of both intake valves (V_I_1, V_I_2)
2. The internal combustion engine according to claim 1, wherein the center timing of the opening angle by a minute amount of _I_2) is set in the latter half of the intake stroke. (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) During the intake stroke mainly in the low-speed operating range of the engine, the pair of intake valves (V__
I_2, V_I_2)
8′), a fuel injection valve (55) capable of evenly injecting fuel toward a pair of intake ports (8) that individually correspond to both intake valves (V_I_1, V_I_2);
In an internal combustion engine, the piston (V_I_2) is equipped with a control means (67) for controlling the operation of the piston ( 4) is provided with a recess (4a) forming a part of the combustion chamber (5) on its surface facing the combustion chamber (5), and the valve train (18, 18') has one intake valve (V_I
The center timing of the opening angle when the intake valve (V_I_2) is in the substantially stopped state is configured to be in the latter half of the intake stroke, and the control means (67) controls when the one intake valve (V_I_2) is in the substantially stopped state. An internal combustion engine characterized in that it is configured to control a fuel injection valve (55) by determining a fuel injection end timing in the first half of an intake stroke. (5) The valve train (18') has one intake valve (V_
I_2) is substantially at rest and the other intake valve (V_I_1) is opened and closed in an opening/closing mode that mainly corresponds to the engine's low-speed operating range;
Claim No. 1 (V_I_1, V_I_2) is configured to be switchable between an opening and closing operation mode mainly corresponding to a high-speed operating range of the engine and a state in which both of them are opened and closed.
Opening of the internal combustion engine described in section 4). (6) An exhaust gas sensor (63) capable of linearly detecting the exhaust gas composition is attached to the exhaust pipe (61), and the exhaust gas sensor (63) is connected to the control means (67) to perform feedback control during lean combustion of the engine. ) The internal combustion engine opener according to claim 4, wherein the internal combustion engine opener is connected to an internal combustion engine. (7) It is connected to a pair of intake valves (V_I_1, V_I_2) and a pair of exhaust valves (V_E_1, V_E_2), and one intake valve (V_I_2) is essentially stopped during the intake stroke mainly in the low-speed operating range of the engine. A valve train (18,
18'), a fuel injection valve (55) capable of evenly injecting fuel toward a pair of intake ports (8) individually corresponding to both intake valves (V_I_1, V_I_2);
control means (67) for controlling the operation of the valve (V_I_2); A recess (4a) forming a part of the combustion chamber (5) is provided on the upper surface of the piston (4) facing the combustion chamber (5) in which the spark plug (45) is disposed in the center. The device (18, 18') has both intake valves (V_I_1
, V_I_2) and both exhaust valves (V_E_1, V_E_
2) has a common single camshaft (19, 19'), and is configured such that the opening angle center timing of one intake valve (V_I_2) in the substantially rest state is in the latter half of the intake stroke, and the control means (67) represents the one intake valve (V_
An internal combustion engine characterized in that when the fuel injection valve (I_2) is in a substantially rest state, the fuel injection valve (55) is controlled by determining the fuel injection end timing in the first half of the intake stroke.