JP2003113723A - Compression ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the starting performance of an internal combustion engine by providing a technique of quickly increasing engine speed at a start-up in a compression ignition type internal combustion engine comprising a variable valve system capable of varying the opening and closing timing and/or lift of an intake valve so as to increase a compression end temperature at a start-up and under a low load. SOLUTION: The compression ignition type internal combustion engine 1 comprises the variable valve system 100 capable of varying the opening and closing timing and/or lift of the intake valves 20 so as to increase a compression end temperature at a start-up and a low load operation and reduce pumping loss under a high load. In a given period within a period from a start-up start to a start-up end, the variable valve system 100 is controlled for reduced pumping loss to lower cranking torque of the internal combustion engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine mounted on a vehicle or the like, and more particularly to start control of a compression ignition type internal combustion engine equipped with a variable valve mechanism.

[0002]

2. Description of the Related Art Generally, in a compression ignition type internal combustion engine (diesel engine), an intake valve is provided for the purpose of preventing a decrease in an excess air ratio at high load, in other words, improving the charging efficiency of intake air at high load. The closing timing of is greatly retarded after the bottom dead center of the intake stroke, and the compression ratio is set high for the purpose of improving startability and combustion efficiency during low load operation.

By the way, in a compression ignition type internal combustion engine having a high compression ratio, it is necessary to increase the strength and rigidity of the cylinder head and the cylinder block. The mass tends to be large, resulting in an increase in weight when mounted on a vehicle, which may be disadvantageous in improving fuel consumption.

On the other hand, a method of lowering the compression ratio of the compression ignition type internal combustion engine can be considered. However, since the in-cylinder atmosphere temperature at the fuel injection timing (near the top dead center of the compression stroke), the so-called compression end temperature, decreases. Incomplete combustion is apt to occur at start-up and at low load, causing white smoke and particulate matter (Particulate Matte
(r: PM) emissions may increase, the fuel consumption rate may deteriorate, or the startability may deteriorate.

Therefore, conventionally, development of a compression ignition type internal combustion engine in which a compression ratio is reduced and a variable valve mechanism is incorporated has been advanced.

In the compression ignition type internal combustion engine having such a low compression ratio, the intake valve opening timing is retarded to after the top dead center of the intake stroke and the intake valve is retarded at the time of low load operation such as idle operation and at the time of starting. Set the valve closing timing near the bottom dead center of the intake stroke, set the intake valve opening timing before the top dead center of the intake stroke and set the intake valve closing timing during medium and high load during steady operation or acceleration operation. The intake stroke is delayed until after BDC.

When the intake valve opening timing is retarded until after the intake stroke top dead center at the time of starting the internal combustion engine or operating at low load,
Since the intake valve is opened with the negative pressure in the cylinder, the speed at which the intake air flows into the cylinder increases, and the kinetic energy of the intake air increases.

Since the kinetic energy of intake air is converted into heat energy in the compression stroke, when the kinetic energy of intake air increases, the heat energy in the cylinder increases,
As a result, the ambient temperature (compression end temperature) in the cylinder near the compression top dead center is increased.

Further, at the time of starting the internal combustion engine and operating at low load, the intake valve closing timing is set near the bottom dead center of the intake stroke, so that the effective compression stroke length is sufficiently secured and the compression end temperature is increased. It will be easier.

Therefore, the intake valve opening timing is retarded until after the intake stroke top dead center and the intake valve closing timing is set near the bottom dead center of the intake stroke during startup of the internal combustion engine and during low load operation. And, it becomes possible to raise the compression end temperature,
As a result, it becomes possible to improve the startability, suppress the emission of PM, and prevent the deterioration of the fuel consumption rate.

On the other hand, when the internal combustion engine is operating at medium and high loads, it is easy to obtain the inertial effect of the intake air. Therefore, the intake valve opening timing is set before the top dead center of the intake stroke, so that the intake pump loss is reduced. It is possible to improve the intake charging efficiency while suppressing the above.

[0012]

In the compression ignition type internal combustion engine having the low compression ratio as described above, the intake valve opening timing is retarded until after the intake stroke top dead center, so that the intake The pump loss of the internal combustion engine during the stroke increases, and the torque required for cranking the internal combustion engine (cranking torque) increases. Furthermore, in the above-described compression ignition type internal combustion engine with a low compression ratio, the closing timing of the intake valve is set near the bottom dead center of the intake stroke at the start, so the effective compression stroke length increases and the cranking torque increases. To do.

When the cranking torque of the internal combustion engine is increased as described above, it becomes difficult to quickly increase the engine speed at the time of starting, so that the load applied to the starter motor is increased and the startability of the internal combustion engine is improved. It may get worse.

Further, when the drive system of the compression ignition type internal combustion engine having the low compression ratio as described above is provided with a resonator such as a flywheel damper, the rotational vibration of the internal combustion engine and the resonator are generated in the middle of the cranking period. May resonate with each other, and in such a case, it is more difficult to increase the engine speed, so that the cranking torque unnecessarily increases and the startability of the internal combustion engine deteriorates. There is.

The present invention has been made in view of the above-mentioned problems, and it is possible to change the opening / closing timing and / or the lift amount of the intake valve so that the compression end temperature becomes high at the time of starting and low load. An object of the present invention is to improve the startability of an internal combustion engine by providing a technique capable of rapidly increasing the engine speed at the time of startup in a compression ignition type internal combustion engine equipped with a variable valve mechanism.

[0016]

The present invention adopts the following means in order to solve the above problems.
That is, the compression ignition type internal combustion engine according to the present invention, the variable valve mechanism for changing the opening and closing timing and the lift amount of the intake valve of the compression ignition type internal combustion engine, when the load of the internal combustion engine is low and at the time of starting, A compression ignition internal combustion engine comprising: a valve operating mechanism control means for controlling a variable valve operating mechanism so that a compression end temperature in a cylinder becomes higher than that when the load of the internal combustion engine is high. During a predetermined period of time from the start to the completion of the start, a start control means is provided for controlling the variable valve mechanism so that the intake pump loss is reduced.

The present invention is provided with a variable valve mechanism capable of changing the opening / closing timing of the intake valve and / or the lift amount so that the compression end temperature is high at the time of starting and low load operation and the pump loss is small at the time of high load. In the ignition type internal combustion engine,
The greatest feature is that the cranking torque of the internal combustion engine is reduced by controlling the variable valve mechanism so that the pump loss is reduced during a predetermined period at the time of starting.

In such a compression ignition type internal combustion engine, the valve operating mechanism control means controls the variable valve operating mechanism so that the compression end temperature becomes high during startup of the internal combustion engine and during low load operation. During operation, the variable valve mechanism is controlled to reduce pump loss.

When the compression end temperature is increased when the load of the internal combustion engine is low, the ignition performance and combustion stability of the fuel are improved, so that the emission amount of particulate matter (PM) and the fuel consumption rate are increased. It is possible to prevent the deterioration.

By the way, when the variable valve mechanism is controlled to raise the compression end temperature at the time of starting the internal combustion engine, the vaporization of the fuel is promoted and the ignitability is improved, but on the other hand, the pump loss is easily increased. Therefore, the cranking torque required for cranking the internal combustion engine increases, and it becomes difficult to increase the engine speed.

On the other hand, in the compression ignition type internal combustion engine according to the present invention, during the predetermined period of the period from the start to the completion of the start of the internal combustion engine, the start time control means is used to reduce the pump loss. The mechanism was controlled.

In this case, the cranking torque of the internal combustion engine decreases during the above-mentioned predetermined period, so that the engine speed rapidly increases.

Here, as the above-mentioned predetermined period, a period from the start of the internal combustion engine until the engine speed becomes equal to or higher than a predetermined speed can be exemplified.

In this case, the cranking torque of the internal combustion engine decreases in the period from the start of the internal combustion engine until the engine speed becomes equal to or higher than the predetermined speed, so that the engine speed rapidly increases after the start of the engine start. Become. After the engine speed has risen to a predetermined value or more, the variable valve mechanism is controlled so that the compression end temperature becomes high, so the fuel ignitability is improved and the internal combustion engine is completely detonated. It will be easier.

As mentioned above, when the variable valve mechanism is controlled so that the pump loss is reduced during the period from the start of the internal combustion engine until the engine speed becomes equal to or higher than the predetermined speed, The fuel injection may be prohibited. This is because when fuel injection is performed under a condition where the engine speed is low and the compression end temperature is low, it is assumed that the fuel will be discharged without burning.

Further, the above-mentioned predetermined period can be exemplified by a period during which the rotational vibration of the internal combustion engine resonates with the resonator provided in the drive system of the internal combustion engine.

This is because if the rotational vibration of the internal combustion engine resonates with the resonator during the startup of the internal combustion engine, the increase of the engine speed may be hindered. In such a case, the compression end temperature becomes high. This is because if the variable valve mechanism is controlled, it becomes more difficult for the engine speed to rise.

Here, as the above-mentioned resonator, a flywheel damper or the like provided on a flywheel of an internal combustion engine can be exemplified.

In the compression ignition type internal combustion engine according to the present invention, the variable valve mechanism includes a low load cam profile formed so that the opening timing of the intake valve is retarded from the top dead center of the intake stroke, It may be configured to be able to select either one of the high load cam profile formed so that the valve opening timing is near the top dead center of the intake stroke,
Alternatively, the cam profile may be continuously changed from the low load cam profile to the high load cam profile.

In this case, the valve mechanism control means selects the low-load cam profile during startup and low-load operation of the internal combustion engine, and selects the high-load cam profile during medium-high load operation of the internal combustion engine. The variable valve mechanism is controlled, but the variable valve mechanism is controlled by the starting control means so as to select the high load cam profile during a predetermined period from the start of the internal combustion engine to the completion of the start. You can do it.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a compression ignition type internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic structure of a compression ignition type internal combustion engine according to the present invention. The internal combustion engine 1 shown in FIG.
It is a water-cooled four-stroke cycle diesel engine having four cylinders 2 and has a relatively low compression ratio.

Each cylinder 2 of the internal combustion engine 1 is provided with two intake valves 20 and two exhaust valves 21, and a fuel injection valve 3 for injecting fuel directly into a combustion chamber (not shown). . Further, each cylinder 2 is provided with an in-cylinder pressure sensor 4 that outputs an electric signal corresponding to the pressure in the cylinder.

Each of the fuel injection valves 3 described above communicates with a pressure accumulating chamber (common rail) 5 for accumulating fuel to a predetermined pressure. A common rail pressure sensor 5a that outputs an electric signal corresponding to the pressure of the fuel in the common rail 5 (common rail pressure) is attached to the common rail 5.

The common rail 5 communicates with a fuel pump 7 via a fuel supply pipe 6. This fuel pump 7
Is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source, and the pump pulley 7a attached to the input shaft of the fuel pump 7 is connected to the output shaft (crankshaft) of the internal combustion engine 1. It is connected to the attached crank pulley 1 a via a belt 8.

In the fuel injection system thus constructed, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 7, the fuel pump 7 is transmitted from the crankshaft to the input shaft of the fuel pump 7. The fuel is discharged at a pressure according to the rotating torque.

The fuel discharged from the fuel pump 7 is
It is supplied to the common rail 5 via the fuel supply pipe 6, accumulated in the common rail 5 to a predetermined pressure, and distributed to the fuel injection valve 3 of each cylinder 2. Then, when a predetermined drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.

Next, an intake branch pipe 9 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 9 communicates with a combustion chamber of each cylinder 2 through an intake port (not shown). . The intake branch pipe 9 is connected to an intake pipe 10, and the intake pipe 10
Is connected upstream to an air cleaner box and an air duct (not shown).

In the middle of the intake pipe 10, the intake pipe 10
An intake throttle valve 60 for restricting the flow rate of intake air flowing therein is attached, and the intake throttle valve 60 is composed of a step motor or the like and drives the intake throttle valve 60 to open and close according to the magnitude of the applied electric power. 61 is attached.

In the intake system configured as described above, the intake air flowing into the air cleaner box is guided to the intake pipe 10 after dust and the like in the intake air are removed by the air cleaner in the air cleaner box. The intake air guided to the intake pipe 10 flows into the intake branch pipe 9 after the flow rate is throttled as necessary by the intake throttle valve 60, and then the intake air of each cylinder 2 is passed through each branch pipe of the intake branch pipe 9. Distributed to ports. When the intake valve 20 opens, the intake air distributed to the intake port is
It is sucked into the combustion chamber of each cylinder 2.

On the other hand, an exhaust branch pipe 11 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 11 communicates with a combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch pipe 11 is connected to an exhaust pipe 12, and the exhaust pipe 12 is connected downstream to an exhaust purification catalyst.

In the exhaust system configured as described above, the air-fuel mixture (burnt gas) burned in each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 11 through the exhaust port, and then the exhaust branch pipe 11 is discharged. Is discharged to the exhaust pipe 12. The exhaust gas that has flowed into the exhaust pipe 12 is released into the atmosphere after being purified by the exhaust purification catalyst downstream of the exhaust pipe 12.

Further, the intake branch pipe 9 and the exhaust branch pipe 11 are communicated with each other via an exhaust gas recirculation passage (EGR passage) 13 for guiding a part of the exhaust gas flowing in the exhaust branch pipe 11 to the intake branch pipe 9. There is. A flow rate control valve (EGR), which is composed of a solenoid valve or the like in the middle of the EGR passage 13, and changes the flow rate of exhaust gas (hereinafter, referred to as EGR gas) flowing in the EGR passage 13 according to the magnitude of the applied power. Valve) 14 is provided.

In the EGR passage 13, the EGR valve 14
An EG flowing in the EGR passage 13 is provided at a more upstream portion.
An EGR cooler 15 that cools the R gas is provided.

In the exhaust gas recirculation mechanism thus constructed, when the EGR valve 14 is opened, the EGR passage 13 is brought into conduction, and a part of the exhaust gas flowing in the exhaust branch pipe 11 is transferred to the EGR passage 13. It flows in and is guided to the intake branch pipe 9 via the EGR cooler 15.

At this time, in the EGR cooler 15, heat exchange is performed between the EGR gas flowing in the EGR passage 13 and a predetermined refrigerant, and the EGR gas is cooled.

The EGR gas recirculated from the exhaust branch pipe 11 to the intake branch pipe 9 through the EGR passage 13 is introduced into the combustion chamber of each cylinder 2 while being mixed with the fresh air flowing from the upstream side of the intake branch pipe 9. Then, the fuel injected from the fuel injection valve 3 is used as an ignition source for combustion.

Here, the EGR gas contains an inert gas component such as water (H ₂ O) and carbon dioxide (CO ₂ ) which does not burn by itself and has an endothermic property. Therefore, when EGR gas is contained in the air-fuel mixture,
The combustion temperature of the air-fuel mixture is lowered, so nitrogen oxides (NO
x) is suppressed.

Further, when the EGR gas is cooled in the EGR cooler 15, the temperature of the EGR gas itself is lowered and the volume of the EGR gas is reduced. Therefore, when the EGR gas is supplied into the combustion chamber, the EGR gas is reduced. The ambient temperature of 1 does not unnecessarily rise, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber does not unnecessarily decrease.

Further, the internal combustion engine 1 according to the present embodiment is provided with the variable valve mechanism 100 for changing the lift amount and working angle of the intake valve 20.

The variable valve mechanism 100 achieves both improvement of drivability and exhaust emission of the internal combustion engine 1 at engine start and low load, and improvement of drivability and exhaust emission of the internal combustion engine 1 at medium and high load. It is a mechanism provided to do this.

In the compression ignition type diesel engine having a low compression ratio, it is easy to obtain the inertia effect of the intake air, and it is easy to increase the charging efficiency of the intake air. Combustion stability can be secured while suppressing the amount of substances (NOx) and soot generated, but the compression end temperature in the low load operating region where the inertial effect of intake air is difficult to obtain and the intake charge efficiency tends to decrease. It is difficult to increase the fuel efficiency, which may lead to deterioration of drivability and deterioration of exhaust emission due to deterioration of ignitability and combustion stability.

The variable valve mechanism 100, as shown in FIG. 2, is fixed to the intake camshaft 30 rotatably supported by the cylinder head of the internal combustion engine 1 and to the cylinder head in parallel with the intake camshaft 30. Rocker shaft 33, rocker arm 34 rotatably supported by rocker shaft 33, and rocker arm 3
The intake valve 20 is opened and closed by the rotation of the valve 4, and a valve spring 200 that biases the intake valve 20 in the valve closing direction.

The intake camshaft 30 is provided with two kinds of cams 31 and 32 having different cam profiles, the same number as the number of cylinders (four in this embodiment). These two types of cams 31 and 32 are used for one cam 3
The profile of No. 1 is formed so that the lift amount and the working angle are larger than the profile of the other cam 32. Hereinafter, the cam 31 will be referred to as a high lift cam 31, and the cam 32 will be referred to as a low lift cam 32.

The rocker shaft 33 is disposed diagonally below the intake cam shaft 30, and the rocker shaft 33 rotatably supports the base end of the rocker arm 34. At that time, it is assumed that the rocker shaft 33 has the same number of rocker arms 34 as the number of cylinders.

An arm 35 is projected from the tip of each rocker arm 34 described above. The distal end of the arm 35 is bifurcated, and the two branched distal ends are in contact with the proximal ends of the two intake valves 20 of each cylinder 2.

Further, as shown in FIG. 3, a movable cam follower 36 capable of contacting the high lift cam 31 and a roller cam follower 37 capable of contacting the low lift cam 32 are provided on the surface of each rocker arm 34. There is.

The roller cam follower 37 is rotatably supported by the rocker arm 34, and the low lift cam 3
The rolling force of the low lift cam 32 is transmitted to the rocker arm 34 while making rolling contact with the rocker arm 34.

The movable cam follower 36 is arranged slidably in the vertical direction with respect to the rocker arm 34.
A coil spring 38 that urges the movable cam follower 36 toward the high lift cam 31 is provided between the movable cam follower 36 and the rocker arm 34.

Here, the rocker arm 34 described above includes
The movable cam follower 36 with respect to the rocker arm 34
A lock mechanism 39 for selectively permitting or restricting (locking) the relative sliding of is provided.

As shown in FIG. 4, the lock mechanism 39 crosses the slide hole 40 and a slide hole 40 that vertically penetrates the rocker arm 34 and slidably supports the movable cam follower 36. A cylinder hole 41 formed in the rocker arm 34, a lock pin 42 slidably fitted in the cylinder hole 41, and the cylinder hole 41.
And a coil spring 43 that is disposed inside and biases the lock pin 42 in a direction away from the sliding hole 40.

A stopper 44 is provided at the end of the lock pin 42 on the sliding hole 40 side. This stopper 4
4, when the lock pin 42 is located at the base end of the cylinder hole 41, most of the stopper 44 is housed in the cylinder hole 41 as shown in FIG. 4, and the lock pin 42 is located at the tip of the cylinder hole 41. When doing so, as shown in FIG. 5, most of the stopper 44 is configured to project into the sliding hole 40.

The space 45 on the base end side defined by the lock pin 42 in the cylinder hole 41 is a hydraulic chamber into which hydraulic oil for sliding the lock pin 42 is introduced. A rocker arm oil passage 46 formed in the rocker arm 34 communicates with the hydraulic chamber 45. The rocker arm oil passage 46 communicates with a rocker shaft oil passage 47 (see FIGS. 1 and 2) formed in the rocker shaft 33.

The rocker shaft oil passage 47 has an oil control valve (OCV) 50 as shown in FIG.
And an oil passage 48. An oil supply passage 51 and an oil return passage 52 are connected to the OCV 50.

The oil supply passage 51 is driven by an electric motor or the like to discharge the working oil.
3, the oil return passage 52 is connected to an oil pan 54 for storing hydraulic oil.

The OCV 50 is the oil supply passage 5
1 or the oil return passage 52 is selectively connected to the oil passage 48. This OCV5
Reference numeral 0 denotes, for example, a solenoid valve, which conducts the oil return passage 52 and the oil passage 48 when a drive current is not applied, and conducts the oil supply passage 51 and the oil passage 48 when a drive current is applied. Let

In the lock mechanism 39 constructed as above, when the drive current is not applied to the OCV 50,
Since the oil passage 48 and the oil return passage 52 are electrically connected, the hydraulic oil in the hydraulic chamber 45 is transferred to the rocker arm oil passage 46 →
The oil is discharged to the oil pan 54 through the rocker shaft oil passage 47, the oil passage 48, and the oil return passage 52.

The hydraulic oil in the hydraulic chamber 45 is transferred to the oil pan 54.
When it is discharged to the base, the lock pin 42 moves to the base end of the cylinder hole 41 under the biasing force of the coil spring 43 (see FIG. 4), and the stopper 44 accordingly. Are accommodated in the cylinder hole 41.

In this case, the movable cam follower 36 becomes slidable in the sliding hole 40. That is, the rocker arm 34
The relative sliding of the movable cam follower 36 with respect to is allowed.

When the movable cam follower 36 is allowed to slide relative to the rocker arm 34, the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is transmitted to the rocker arm 34 via the coil spring 38. .

At this time, since the urging force of the coil spring 38 is set sufficiently smaller than the urging force of the valve spring 200, the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is the coil spring 38.
Is expanded and contracted (in other words, the sliding motion of the movable cam follower 36) is absorbed. In other words, a force larger than the urging force of the valve spring 200 is not transmitted from the high lift cam 31 to the rocker arm 34.

As a result, the rocker arm 34 is swung by the pressing force transmitted from the low lift cam 32 to the roller cam follower 37, and the rocker arm 34 is rocked.
The intake valve 20 is driven to open and close with the swinging of the. That is, the intake valve 20 is driven to open and close according to the cam profile shape of the low lift cam 32.

On the other hand, when the drive current is applied to the oil pump 53 and the OCV 50, the oil pump 53 discharges the working oil and the oil passage 48 and the oil supply passage 51 are electrically connected to each other, so that the oil pump 53 discharges the oil. The selected hydraulic oil is supplied to the hydraulic chamber 45 via the oil supply passage 51 → the oil passage 48 → the rocker shaft oil passage 47 → the rocker arm oil passage 46.

From the oil pump 53 to the hydraulic chamber 45
When the hydraulic oil is supplied to the hydraulic chamber 45, the hydraulic pressure in the hydraulic chamber 45 rises, so that the lock pin 42 moves to the tip of the cylinder hole 41 against the urging force of the coil spring 43 (see FIG. 5). As a result, the stopper 44 projects into the sliding hole 40.

In this case, since the bottom surface of the movable cam follower 36 is in contact with the stopper 44 when the movable cam follower 36 is displaced to the uppermost position, the relative sliding of the movable cam follower 36 with respect to the rocker arm 34 is restricted (locked). Become.

When the relative sliding of the movable cam follower 36 to the rocker arm 34 is restricted (locked), the pressing force transmitted from the high lift cam 31 to the movable cam follower 36 is applied to the rocker arm 34 via the stopper 44 and the lock pin 42. It will be transmitted.

As a result, the rocker arm 34 moves from the high lift cam 31 to the movable cam follower 36 and the lock pin 42.
Since the rocker arm 34 is swung by the pressing force transmitted to the intake valve 20, the intake valve 20 is opened and closed. That is, the intake valve 20 has the high lift cam 31.
It is driven to open and close according to the cam profile shape.

Here, in the cam profile of the high lift cam 31 described above, for example, as shown by the solid line in FIG. 6, the opening timing of the intake valve 20 is the top dead center of the intake stroke (TDC: TOP).
2 ° earlier than DEADCENTER) (BTDC 2 °, BTDC: BEFOR
E TOP DEAD CENTER), and the closing timing of the intake valve 20 is 30 ° later than the intake stroke bottom dead center (BDC: BOTTOM DEAD CENTER) (ABDC 30 °, ABDC: AFTER BOTTOM DEAD
CENTER).

When the high lift cam 31 formed in this way is selected, the intake valve 20 opens immediately before the top dead center of the intake stroke, so that the pump loss of intake air is reduced and the intake valve is Since the valve is closed much later than the bottom dead center of the stroke, it is easy to improve the intake charging efficiency by utilizing the inertial effect of intake air.

Therefore, if the high lift cam 31 is selected in the medium and high load operation region where the intake inertia effect is easily obtained, it is possible to prevent the engine output from being decreased due to the decrease of the pump loss, and the intake inertia effect is achieved. This makes it possible to increase the intake charging efficiency.

On the other hand, the cam profile of the low lift cam 32 is, for example, as shown by the broken line in FIG. 6, when the opening timing of the intake valve 20 is 60 ° later than the top dead center of the intake stroke (ATDC60 °), In addition, it is assumed that the closing timing of the intake valve 20 is 20 ° later than the bottom dead center of the intake stroke (ABDC 20 °).

When the low lift cam 32 formed in this way is selected, the intake valve 20 opens in the middle of the intake stroke, so that when the intake valve 20 opens, the inside of the cylinder 2 has a negative pressure. Then, the intake air vigorously flows into the cylinder 2. Further, since the intake valve 20 is closed relatively early after the bottom stroke of the intake stroke, the effective compression stroke length is increased, and the pressure in the cylinder 2 can be increased.

Therefore, if the low lift cam 32 is selected in the low load operation region where it is difficult to obtain the inertial effect of the intake air and the charging efficiency of the intake air is likely to be low, the compression end temperature can be increased and the vaporization and ignition of the fuel can be achieved. It is possible to improve the property.

Returning to FIG. 1, the internal combustion engine 1 is provided with an electronic control unit (ECU) 18 for controlling the operating state of the internal combustion engine 1. The ECU 18 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request, and is configured as an arithmetic logic operation circuit including a CPU, a ROM, a RAM, a backup RAM, and the like. Has been done.

The ECU 18 includes the in-cylinder pressure sensor 4 described above.
In addition to the common rail pressure sensor 5a, a crank position sensor 1 that outputs a pulse signal each time the crankshaft of the internal combustion engine 1 rotates by a predetermined angle (for example, 10 °).
6. A water temperature sensor 17, which outputs an electric signal corresponding to the temperature of the cooling water circulating in the water jacket of the internal combustion engine 1,
An accelerator opening sensor 19 that outputs an electric signal corresponding to the operation amount of the accelerator pedal is electrically connected, and output signals of various sensors are input to the ECU 18.

Further, the ECU 18 has the fuel injection valves 3, E
The GR valve 14, the OCV 50 and the oil pump 53 of the variable valve mechanism 100 are electrically connected, the star motor 300 attached to the internal combustion engine 1 is electrically connected, and the output signal of the ECU 18 causes the fuel injection described above. Inputs are made to the valve 3, the EGR valve 14, the variable valve mechanism 100, and the starter motor 300.

The ECU 18 having the above-mentioned configuration is
According to various application programs stored in advance in M, in addition to known control such as fuel injection control, EGR control, valve control, etc., start-up control which is the gist of the present invention is executed.

Hereinafter, the start-up control will be described with reference to FIGS. First, in normal valve drive control, the ECU 1
When the internal combustion engine 1 is in a low load operation state such as an idle operation state or at the time of starting, the reference numeral 8 stops the application of the drive current to the OCV 50 and the oil pump 53 in order to open / close the intake valve 20 by the low lift cam 32. Further, when the internal combustion engine 1 is in the steady operation state or the acceleration operation state, the ECU 18 causes the high lift cam 31 to move the intake valve 20.
A drive current is applied to the OCV 50 and the oil pump 53 in order to drive the open / close operation.

As described above, when the high lift cam 31 is selected in the medium and high load operation range of the internal combustion engine 1, it becomes possible to improve the intake charging efficiency while suppressing the pump loss. On the other hand, when the low lift cam 32 is selected at the time of starting the internal combustion engine 1 or in the low load operation region, the compression end temperature rises, so that it becomes possible to improve the ignitability and combustion stability of the fuel.

By the way, when the low lift cam 32 is selected, the opening timing of the intake valve 20 is retarded until after the top dead center of the intake stroke, so that the compression end temperature rises as shown in FIG. On the other hand, the pump loss of the internal combustion engine 1 increases. Further, when the low lift cam 32 is selected, the intake valve 2
Since the valve closing timing of 0 is set near the bottom dead center of the intake stroke,
The effective compression stroke length becomes longer.

Therefore, when the low lift cam 32 is selected at the time of starting the internal combustion engine 1, the torque required for cranking the internal combustion engine 1 (cranking torque) is increased due to the increase of the pump loss and the effective compression stroke length. ) Increases, and it becomes difficult to quickly increase the engine speed at the time of starting, and as a result, the startability of the internal combustion engine may deteriorate.

Therefore, in the starting control according to the present embodiment, the ECU 18 controls the intake valve 20 by the high lift cam 31 during the period from the start of the internal combustion engine 1 until the engine speed becomes equal to or higher than the predetermined engine speed: NE1. The variable valve mechanism 100 is controlled to be opened and closed.

When the high lift cam 31 is selected in the period from the start of the internal combustion engine 1 until the engine speed becomes equal to or higher than the predetermined engine speed: NE1 as described above, the pump loss in that period is reduced and the effective compression stroke is reduced. Since the length is shortened and the cranking torque is reduced accordingly,
The engine speed will quickly increase.

When the variable valve mechanism 100 is controlled to open / close the intake valve 20 by the low lift cam 32 after the engine speed has risen to a predetermined speed: NE1 or more, the compression end temperature of each cylinder 2 is controlled. Is preferably increased, and the ignitability of fuel is improved.

Further, in the control at the time of starting in the present embodiment, the ECU 18 controls the engine from the start of the internal combustion engine 1 until the engine speed becomes equal to or higher than the predetermined speed NE1.
Execution of fuel injection was prohibited. This is because if fuel injection is performed in a situation where the engine speed is low and the compression end temperature is low, the fuel may remain in the cylinder 2 without burning or be discharged into the atmosphere. is there.

When such a start control is executed, FIG.
As shown in, the engine speed increases more rapidly than when the low lift cam 32 is selected during the entire period from the start of the internal combustion engine 1 to the completion of the start. It can be shortened.

Next, the starting control in the present embodiment will be concretely described with reference to FIG. FIG. 9 is a flowchart showing the control routine at the time of starting. The startup control routine is a routine stored in advance in the ROM, and is a routine executed by the ECU 18 triggered by the switching of an ignition switch (not shown) from off to on.

In the start-up control routine, the ECU 18
First, in S901, it is determined whether or not the starter switch is turned on.

If it is determined in S901 that the starter switch is off, the ECU 18 proceeds to S90 until the starter switch is switched from off to on.
The process 1 is repeatedly executed.

On the other hand, if it is determined in S901 that the starter switch is on, the ECU 18
Proceeding to S902, the OCV 50 and the oil pump 53 are controlled so that the intake valve 20 is opened and closed by the high lift cam 31.
Drive power is applied to.

In S903, the ECU 18 applies drive power to the starter motor 300.

In S904, the ECU 18 calculates the actual engine speed: Ne based on the output signal of the crank position sensor 16, and the engine speed: Ne is the predetermined engine speed: Ne.
Determine whether it is NE1 or higher.

Actual engine speed in S904:
When it is determined that Ne is less than the predetermined rotation speed: NE1,
The ECU 18 determines that the actual engine speed: Ne is the predetermined engine speed: NE.
The processing of S904 is repeatedly executed until the temperature rises to 1 or more.

When the actual engine speed: Ne rises above the predetermined engine speed: NE1, the ECU 18 causes S90
5, the application of drive power to the OCV 50 and the oil pump 53 is stopped, and the intake valve 20 is set to the low lift cam 32.
To be opened and closed by.

In step S906, the ECU 18 starts applying drive power to the fuel injection valve 3. When the process of S906 is completed, the ECU 18 ends the execution of this routine.

In this way, the ECU 18 executes the control routine at the time of starting, whereby during the period from the start to the completion of the start of the internal combustion engine 1, the engine speed from the start to the engine speed Ne.
Since the intake valve 20 is driven to be opened and closed by the high lift cam 31 until the engine speed becomes equal to or higher than the predetermined engine speed: NE1, it is possible to increase the engine speed: Ne at an early stage after the start of the start. . And engine speed: Ne
Since the intake valve 20 is opened and closed by the low lift cam 32 after the engine speed rises to a predetermined speed: NE1 or more, the compression end temperature in the cylinder 2 is suitably increased, and as a result, the internal combustion engine 1 is quickly operated. As a result, the internal combustion engine 1 is improved in startability.

<Other Embodiments> Next, another embodiment of the compression ignition type internal combustion engine according to the present invention will be described with reference to FIGS. Here, the configuration different from the above-described embodiment will be described, and the description of the same configuration will be omitted.

In an internal combustion engine mounted on a vehicle, a technique of attaching a flywheel damper to a flywheel of the internal combustion engine is prevailing for the purpose of mitigating an impact caused by acceleration and deceleration of the internal combustion engine on a drive wheel. This flywheel damper allows the displacement of the engine output shaft (crankshaft) with respect to the drive wheel in the acceleration / deceleration direction by bending itself, thereby mitigating the shock associated with the acceleration / deceleration.

However, when the engine speed is extremely low, such as when the internal combustion engine is started, the flywheel damper may resonate with the rotational vibration of the internal combustion engine, causing hunting in the engine speed. In this way, if the engine speed hunts during starting, it becomes difficult for the engine speed to rise quickly.

For this reason, when the flywheel damper is attached to the flywheel of the internal combustion engine 1 according to the above-described embodiment, as shown in FIG. In the rotation region (NE2 to NE3 in the figure) where the flywheel damper resonates, the increase in the engine speed temporarily stops (period in the figure: t).

Therefore, in the present embodiment, in addition to the period from the start of the internal combustion engine 1 until the engine speed: Ne rises above the predetermined speed: NE1, the rotational vibration of the internal combustion engine 1 and the flywheel damper are In the resonating period, the intake valve 2
0 is opened and closed by the high lift cam 31.

Specifically, the lower limit value of the engine speed at which the rotational vibration of the internal combustion engine 1 resonates with the flywheel damper (hereinafter referred to as the resonance lower limit speed): NE2 and the upper limit value (hereinafter, referred to as the resonance lower limit speed).
The resonance upper limit rotational speed): NE3 is experimentally obtained in advance, and the first period from the start of the internal combustion engine 1 until the engine rotational speed: Ne becomes equal to or higher than the predetermined rotational speed: NE1 and the engine rotational speed. The intake valve 20 is driven to be opened and closed by the high lift cam 31 in a second period in which the number: Ne is within the range of the resonance lower limit rotation speed: NE2 or more and the resonance upper limit rotation speed: NE3 or less.

When the intake valve 20 is opened / closed by the high lift cam 31 in the second period during which the rotational vibration of the internal combustion engine 1 resonates with the flywheel damper, the internal combustion engine 1 is closed and opened during the second period. Since the ranking torque is reduced, the engine speed rapidly increases without delay as shown in FIG.

Hereinafter, the starting control in this embodiment will be specifically described with reference to FIG. FIG. 11 is a flowchart showing the control routine at the time of starting. The start-up control routine is a routine stored in the ROM in advance, and is triggered by the switching of an ignition switch (not shown) from off to on.
8 is a routine to be executed.

In the start-up control routine, the ECU 18
First, in S1101, it is determined whether or not the starter switch is turned on.

[0116] If it is determined in S1101 that the starter switch is off, the ECU 18 proceeds to S110
The process 1 is repeatedly executed.

On the other hand, if it is determined in S1101 that the starter switch is on, the ECU 18
Proceeding to S1102, the OCV 50 and the oil pump 53 are controlled so that the intake valve 20 is opened and closed by the high lift cam 31.
Drive power is applied to.

In S1103, the ECU 18 applies drive power to the starter motor 300.

In step S1104, the ECU 18 calculates the actual engine speed: Ne based on the output signal of the crank position sensor 16, and the engine speed: Ne is the predetermined engine speed: Ne.
Determine whether it is NE1 or higher.

Actual S1104 engine speed: N
If it is determined that e is less than the predetermined rotation speed: NE1, E
In the CU 18, the actual engine speed: Ne is the predetermined engine speed: NE1
The processing of S1104 is repeatedly executed until the temperature rises above the above.

When the actual engine speed: Ne rises above the predetermined engine speed: NE1, the ECU 18 determines in S1105.
Then, the application of drive power to the OCV 50 and the oil pump 53 is stopped, and the intake valve 20 is opened and closed by the low lift cam 32.

In S1106, the ECU 18 starts applying drive power to the fuel injection valve 3.

In S1107, the ECU 18 calculates the actual engine speed: Ne at the present time based on the output signal of the crank position sensor 16, and the engine speed: Ne.
It is determined whether Ne is the resonance lower limit rotation speed: NE2 or more.

If it is determined in S1107 that the engine speed: Ne is less than the resonance lower limit speed: NE2, E
The CU 18 repeatedly executes the processing of S1107 until the engine speed: Ne becomes equal to or higher than the resonance lower limit speed: NE2.

Then, when the engine speed: Ne rises to the resonance lower limit speed: NE2 or more, the ECU 18 determines in S110.
8, the driving power is applied to the OCV 50 and the oil pump 53 so that the intake valve 20 is opened and closed by the high lift cam 31.

In S1109, the ECU 18 calculates the actual engine speed: Ne at the present time based on the output signal of the crank position sensor 16, and the engine speed: Ne.
It is determined whether Ne is higher than the resonance upper limit rotation speed: NE3.

If it is determined in S1109 that the engine speed: Ne is equal to or lower than the resonance upper limit speed: NE3, E
The CU 18 repeatedly executes the processing of S1109 until the engine speed: Ne becomes higher than the resonance upper limit speed: NE3.

When the engine speed: Ne becomes higher than the resonance upper limit speed: NE3, the ECU 18 proceeds to S1110 to stop the application of the drive power to the OCV 50 and the oil pump 53, and the intake valve 20 causes the low lift cam 32 to move. To be opened and closed by.

In this way, the ECU 18 executes the control routine at the time of starting, so that the engine speed: Ne from the start of the engine in the period from the start to the completion of the start of the internal combustion engine 1.
In addition to the first period until the engine speed becomes equal to or higher than NE1, the intake valve 20 is opened and closed by the high lift cam 31 in the second period in which the rotational vibration of the internal combustion engine 1 and the flywheel damper resonate. Therefore, the engine speed quickly increases during the first and second periods described above. As a result, the complete combustion of the internal combustion engine 1 is likely to occur early, and the period from the start of the start of the internal combustion engine 1 to the completion of the start of the internal combustion engine 1 can be shortened.

[0130]

In the compression ignition type internal combustion engine according to the present invention,
In a compression ignition internal combustion engine equipped with a variable valve mechanism that can change the intake valve opening / closing timing and / or the lift amount so that the compression end temperature is high during startup and low load operation and pump loss is reduced under high load Since the variable valve mechanism is controlled so that the pump loss is reduced during a predetermined period of the period from the start to the completion of the start, the cranking torque during the predetermined period is decreased and the engine speed is rapidly increased. Like Therefore, according to the compression ignition type internal combustion engine of the present invention, the engine speed can be rapidly increased at the time of starting, so that the internal combustion engine can be quickly started, and thus the internal combustion engine is started. Will be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a compression ignition type internal combustion engine according to an embodiment.

FIG. 2 shows a configuration of a variable valve mechanism (1)

FIG. 3 is a diagram showing a configuration of a variable valve mechanism (2).

FIG. 4 is a diagram showing a configuration of a lock mechanism.

FIG. 5 is a diagram for explaining the operation of the lock mechanism.

FIG. 6 is a diagram showing cam profiles of a high lift cam and a low lift cam.

FIG. 7 is a diagram showing how the compression end temperature and the pump loss change as the intake valve opening timing changes.

FIG. 8 is a diagram (1) showing the relationship between the control state of the variable valve mechanism and the engine speed when the internal combustion engine is started.

FIG. 9 is a flowchart showing a control routine at the time of starting.

FIG. 10 is a diagram (2) showing the relationship between the control state of the variable valve mechanism and the engine speed when the internal combustion engine is started.

FIG. 11 is a diagram showing a control routine at start-up according to another embodiment.

[Explanation of symbols]

1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... In-cylinder pressure sensor 13 ... EGR passage 14 ... EGR passage 18 ... ECU 20 ... Intake valve 100 ... Variable valve mechanism 300 ... Starter motor

Continued front page    F-term (reference) 3G018 AA11 AB04 AB16 BA16 CA19                       DA10 DA18 DA50 DA51 EA02                       EA11 EA21 FA02 FA06 FA07                       GA11                 3G092 AA02 AA06 AA11 AA17 DA01                       DA04 DG05 EA03 EA04 EA27                       FA31 GA01 HA11Z HE01Z                 3G301 HA02 HA04 HA06 HA13 HA19                       KA01 LA07 LB04 LC08 NA08                       NC02 NE23 PC01Z PE01Z                       PE03Z PF03Z PF16Z

Claims (4)

[Claims] 1. A variable valve mechanism for changing the opening / closing timing and / or lift amount of an intake valve of a compression ignition type internal combustion engine, and when the load of the internal combustion engine is low and when the internal combustion engine is started, when the load of the internal combustion engine is high. In comparison, in a compression ignition type internal combustion engine including a valve operating mechanism control means for controlling a variable valve operating mechanism so that a compression end temperature in a cylinder becomes higher, a period from the start to the end of the start of the internal combustion engine. A compression ignition internal combustion engine characterized by comprising a start control means for controlling the variable valve mechanism so as to reduce pump loss for a predetermined period of time. 2. The compression ignition type internal combustion engine according to claim 1, wherein the predetermined period is a period from the start of cranking of the internal combustion engine until the engine speed reaches or exceeds a predetermined speed. 3. The compression ignition type internal combustion engine according to claim 1, wherein the predetermined period is a period in which the rotational vibration of the internal combustion engine resonates with a resonator provided in a drive system of the internal combustion engine. organ. 4. The variable valve mechanism comprises a low load cam profile formed so that the opening timing of the intake valve is retarded from the top dead center of the intake stroke, and the opening timing of the intake valve is set to the upper intake stroke. One of a high load cam profile formed near the dead center is selectable, and the valve mechanism control means controls the low load when the load of the internal combustion engine is low and when the engine is started. A cam profile is selected, and the variable valve mechanism is controlled to select the high load cam profile when the load of the internal combustion engine is high, and the start-time control means starts the start of the internal combustion engine and completes the start. The compression ignition type internal combustion engine according to claim 1, wherein the variable valve mechanism is controlled so as to select the high load cam profile for a predetermined period of time up to.