JP4296832B2 - Internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine, and more particularly to a system that cools a piston or a cylinder by oil injection.
[0002]
[Prior art]
Various types of fuel injection methods for internal combustion engines are known from a mechanical or control standpoint. As one of them, after injecting fuel to be burned in order to obtain output in a cylinder, a pause time is set. In some cases, during the expansion stroke or the exhaust stroke, fuel is injected further, so-called post-injection such as post injection is performed.
[0003]
Reasons for performing such secondary fuel injection are as follows: (1) When the engine is in a specific operating state, the secondary fuel injection is performed during the expansion stroke to increase the pressure of the exhaust gas and increase the output of the supercharger. (2) After the main fuel injection, the auxiliary fuel is injected just before the exhaust valve is closed and burnt, so that the temperature of the exhaust gas is raised and captured by the filter provided in the exhaust passage. (3) NOx is reduced by activating a NOx reduction catalyst provided in the exhaust system with the fuel injected with the auxiliary fuel, promotion of warming up of the catalyst, and the like.
[0004]
By the way, the main fuel injection described above is performed when the piston in the cylinder is in the vicinity of the top dead center, and the sub fuel injection is generally performed in a state where the piston is being lowered. When the piston is near the top dead center, the volume of the combustion chamber is the smallest, and the cylinder wall surface is hidden by the piston.
[0005]
On the other hand, at the time of sub fuel injection, since the piston is lowered, the cylinder wall surface is exposed.
[0006]
From the viewpoint of cylinder wall lubrication, there is no problem because the oil film on the cylinder wall will not be diluted even when fuel is injected during the main fuel injection. The oil film will be diluted with fuel, and lubrication may deteriorate and cause bore flushing.
[0007]
Therefore, the applicant of the present application previously proposed the one shown in Patent Document 1. This is because the fuel injection timing, fuel injection amount, and fuel injection pressure are controlled in accordance with parameters that correlate with the fuel adhesion amount on the cylinder inner wall in the sub fuel injection and pilot injection (performed before the main fuel injection) of the fuel. Is designed to avoid sticking to the cylinder wall as much as possible.
[0008]
Further, in the one shown in Patent Document 2 relating to the application of the present applicant, the sub fuel injection timing based on the compression top dead center is set to the internal fuel injection timing when the temperature in the cylinder reaches the target temperature as the sub fuel injection timing. A sub fuel injection timing determining means that is determined according to the operating state of the engine, and configured to perform the sub fuel injection when the in-cylinder temperature reaches a desired target temperature by the sub fuel injection timing determining means. Is.
[0009]
When the target temperature is set as an in-cylinder temperature at which the fuel injected by the auxiliary fuel does not burn and the spray does not reach the cylinder wall surface of the cylinder, the fuel spray injected by the auxiliary fuel is injected into the cylinder wall surface of the cylinder. As a result, the engine oil can be prevented from being diluted due to the auxiliary fuel injection.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-50897 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-45828
[Problems to be solved by the invention]
However, it is difficult to effectively prevent oil from adhering to the cylinder wall surface by any of the methods described above.
[0012]
That is, the timing of the auxiliary fuel injection, the amount of fuel, and the like are limited to an ideal narrow range because of demands for preventing fluctuations in output of the internal combustion engine and deterioration of exhaust emissions. In the auxiliary fuel injection in this range, there is a possibility that it is impossible to execute at an ideal timing or injection amount for the purpose of ensuring lubrication of the cylinder. In other words, the various conditions of the auxiliary fuel injection must be set as a compromise between the allowable range for executing the injection and ensuring the cylinder lubrication, and there is a possibility that satisfactory characteristics cannot be obtained.
[0013]
The present invention has been made to solve such a conventional problem, and provides an internal combustion engine capable of performing post fuel injection within an allowable range and at the same time ensuring lubrication of a cylinder wall surface. Let it be an issue.
[0014]
[Means for Solving the Problems]
In order to solve the above-described technical problem, the internal combustion engine of the present invention is configured as follows.
[0015]
A fuel injection valve for injecting fuel into the cylinder;
An oil jet device that performs oil injection for cooling toward at least one of the piston or the cylinder,
In the internal combustion engine capable of sub fuel injection executed during main fuel injection and expansion stroke, exhaust stroke to the fuel injection valve,
When the sub fuel injection is executed, oil injection by the oil jet device is prohibited.
[0016]
The oil jet device is intended to cool the portion by injecting cooling oil into the piston or cylinder by oil injection. Particularly, it is employed for reducing the thermal load in a supercharged internal combustion engine or the like.
[0017]
During sub fuel injection, the prohibition of oil injection by such an oil jet device increases the in-cylinder temperature or suppresses the decrease in the in-cylinder temperature, thereby promoting the evaporation of the fuel supplied by the auxiliary fuel injection. Oil dilution is prevented. At the same time, the original purpose such as an increase in exhaust temperature due to the auxiliary fuel injection is also achieved. Here, the sub fuel injection includes all of the fuel injection executed during the expansion stroke and the exhaust stroke of the engine separately from the main injection, for example, post injection is a typical one.
[0018]
The present invention also provides a fuel injection valve that injects fuel into a cylinder;
An oil injection unit that injects cooling oil onto at least one of the piston back surface and the cylinder;
An injection control unit that controls the operation and stop of the oil injection unit, while causing the fuel injection valve to perform main fuel injection and post fuel injection that is injected later than the main fuel injection,
The injection control unit can be configured to stop the oil injection in the oil injection unit for a predetermined time in synchronization with the post fuel injection timing.
[0019]
The injection control unit includes a programmable microcomputer and stops oil injection in the oil injection unit for a predetermined time in synchronization with the post fuel injection timing. Note that synchronization does not necessarily mean that fuel injection timing and oil injection are stopped at the same time, but can be both positive and negative, taking into account mechanical operation delays and heat conduction delays in the oil injection part. The one with
[0020]
In this way, by stopping the oil injection in the oil injection portion for a predetermined time in synchronization with the post fuel injection timing, the post fuel injection timing, that is, the time when the exposed area of the cylinder wall surface in the cylinder is in an expanded state. Then, the injection of the cooling oil is stopped.
[0021]
As the oil injection stops, the temperature of the piston and cylinder wall surfaces that have been cooled by the oil injection until then increases. In this state, since post fuel injection is performed in the cylinder, the fuel rapidly evaporates in the increased cylinder temperature atmosphere, and adhesion to the cylinder wall surface is suppressed.
[0022]
In this way, the fuel adhesion to the cylinder wall surface is suppressed, so that the oil that should remain on the cylinder wall surface is less diluted, and bore flushing is prevented.
[0023]
The injection control unit is provided with various sensors that measure the accelerator opening, the engine speed, the vehicle speed, the engine operating state of the engine load, or the intake air temperature, exhaust temperature, catalyst inlet temperature, cooling water temperature, and external air pressure. The presence or absence of post fuel injection can be controlled based on at least one of the signals. As described above, it is not always necessary to execute the post fuel injection, and it is selected according to various conditions including the operation state and the like, and parameters for that are obtained from the various sensors. Is preferred.
[0024]
It is preferable that the oil injection in the oil injection unit is controlled by a solenoid valve. The oil injection can be controlled by intermittently energizing the electromagnetic valve. The solenoid valve is suitable for controlling oil injection because of its quick control response and easy wiring and control.
[0025]
The present invention is applicable to a direct-injection diesel engine or gasoline engine. According to the present invention, fuel injection by sub fuel injection is suppressed by prohibiting oil injection and suppressing a decrease in in-cylinder temperature. Can be promoted to reduce fuel adhesion to the cylinder liner. As a result, oil drop due to the attached fuel is prevented.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the internal combustion engine of the present invention will be described in more detail with respect to the embodiment shown in FIGS.
[0027]
The internal combustion engine 1 is a water-cooled four-cycle diesel engine having four cylinders 2. The internal combustion engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure.
[0028]
The common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5. The fuel pump 6 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the internal combustion engine 1 as a drive source. A pump pulley (not shown) attached to the input shaft of the fuel pump 6 is an output shaft of the internal combustion engine 1. It is connected to a crank pulley attached to the (crankshaft).
[0029]
In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to the pressure.
[0030]
The fuel discharged from the fuel pump 6 is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 up to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, it opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0031]
Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port.
[0032]
The intake branch pipe 8 is connected to an intake pipe 9. An air flow meter 11 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake pipe 9 is attached to the intake pipe 9.
[0033]
The intake pipe 9 located between the air flow meter 11 and the intake throttle valve 13 is provided with a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 that operates using exhaust energy as a drive source.
[0034]
The intake pipe 9 is connected to a supercharger 15 via an intercooler 16.
[0035]
In the intake system configured as described above, the intake air flows into the compressor housing 15 a via the intake pipe 9.
[0036]
The intake air flowing into the compressor housing 15a is compressed by the rotation of the compressor wheel built in the compressor housing 15a. The intake air compressed in the compressor housing 15a is adjusted in flow rate by the intake throttle valve 13 as necessary and flows into the intake branch pipe 8. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chambers of the respective cylinders 2 through the respective branch pipes, and burned using the fuel injected from the fuel injection valves 3 of the respective cylinders 2 as an ignition source.
[0037]
On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with the combustion chamber of each cylinder 2 via an exhaust port.
[0038]
The exhaust branch pipe 25 is connected to the turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15b is connected to an exhaust pipe 19, and the exhaust pipe 19 communicates with the atmosphere downstream.
[0039]
FIG. 2 shows an outline of the structure of a cylinder of the internal combustion engine, and FIG. 3 shows an oil circulation path in the internal combustion engine.
[0040]
A fuel injection valve 3 for injecting fuel into the cylinder 2 is provided at the zenith of the cylinder 2. A piston 30 is provided in the cylinder 2, and an oil injection portion 31 that injects cooling oil toward the back surface of the piston 30 is provided below the piston 30. An intake valve 32 and an exhaust valve 33 are provided on the zenith side of the cylinder 2.
[0041]
The fuel injection valve 3 is configured such that the fuel injection timing and the injection amount are controlled by a fuel control unit 35 connected to the fuel system 34.
[0042]
The oil injection section 31 is provided in the oil circulation path shown in FIGS. In the oil circulation path, the oil collected in the oil pan 42 is first sent to the main oil hole 47 through the oil strainer 43, the oil pump 44, the oil cooler 45, and the oil filter 46. The oil is fed from the main oil hole 47 to the valve operating mechanism 50 such as the camshaft 49 through the head oil hole 48.
[0043]
Further, the oil is fed from the main oil hole 47 to the crank journal 51 and the supercharger (turbo) 15. The oil injection unit 31 is connected to the main oil hole 47 via the electromagnetic valve 52. The electromagnetic valve 52 is for opening and closing the orifice of the oil injection unit 31 and is controlled by an electronic control unit (ECU) 55.
[0044]
The ECU 55 is an electronic control unit and incorporates a microcomputer to control the electromagnetic valve 52, the fuel injection valve 3 and other devices in accordance with a pre-programmed sequence. The ECU 55 is connected with a vehicle speed sensor 60, a crank position 33, an accelerator opening sensor 36, and other various sensors such as intake air temperature, exhaust temperature, catalyst inlet temperature, cooling water temperature, and the like. Thus, the main fuel injection condition and the post fuel injection condition in the fuel injection valve 3 are determined.
[0045]
In addition, the ECU 55 controls the electromagnetic valve 52 in synchronization with the post fuel injection, and performs control to temporarily stop the cooling oil injected from the oil injection unit 31.
[0046]
A series of these operations will be described with reference to the flowchart shown in FIG. 4. At least signals from the vehicle speed sensor 60, the crank position sensor 33, and the accelerator opening sensor 36 in the ECU 55 (represented by SPD, NE, and ACCP in the figure), respectively. The process proceeds to step S101. Subsequently, the process proceeds to step S102, where it is determined whether or not to perform post fuel injection based on signals from the various sensors described above.
[0047]
In the case of post fuel injection, when the exhaust gas pressure is increased and the output of the turbocharger is increased to improve the engine output, the post injection is performed immediately after the main fuel injection and immediately before the exhaust valve is closed and burned. In the case where the temperature of the exhaust gas is raised and the particulate matter trapped by the particulate filter is incinerated, the NOx catalyst provided in the exhaust system is activated by the post-injected fuel and NOx is reduced. In some cases, SOx poisoning recovery processing of the catalyst is performed.
[0048]
If the ECU 55 determines that post fuel injection is performed in step S102, the process proceeds from the affirmative branch (Y) to step S103. In step S103, the solenoid valve 52 is turned off, that is, oil injection is stopped. On the other hand, when the post fuel injection is not performed in step S102 based on the determination of the ECU 55, the process proceeds from the negative branch (N) to step S104. In step S104, the solenoid valve 52 is turned on and oil injection is performed.
[0049]
In either case of step S103 or step S104, the process proceeds to return, and monitoring is always continued.
[0050]
Thus, cooling oil injection stops only when post fuel injection is performed. Therefore, in the operation mode without post fuel injection, the temperature of the piston or cylinder wall that has been cooled by the oil injection increases.
[0051]
In this case, since the in-cylinder temperature also rises, post fuel injection is performed in the cylinder 1 in a high temperature atmosphere. Therefore, the fuel evaporates rapidly, evaporates before reaching the cylinder wall surface, and is prevented from adhering to the cylinder wall surface.
[0052]
In this way, since fuel is prevented from adhering to the cylinder wall surface, oil that should remain on the cylinder wall surface is not diluted, and bore flushing is prevented.
[0053]
Although a temporary increase in the temperature around the piston raises the concern that there may be a problem in terms of durability, the graph shown in FIG. In this graph, the engine torque (load amount) is shown on the vertical axis, and the engine speed is shown on the horizontal axis. In the figure, the upper line graph shows the full load characteristic, and the lower hatched area shows the post injection area.
[0054]
Since post fuel injection is performed in a partial region where the catalyst inlet temperature is low, it is always under a condition lower than the maximum load, and even if the piston cooling is temporarily stopped, there is no influence on durability or reliability.
[0055]
Further, mechanically, it is only necessary to provide the electromagnetic valve 52 between the oil injection section 31 and the oil circulation path, so that it can be implemented at a low cost.
[0056]
As described above, in the present embodiment, it is possible to prevent the fuel from adhering to the cylinder wall surface and diluting the oil while performing the post fuel injection under an appropriate condition. Therefore, it is possible to provide an internal combustion engine in which both conditions are compatible, the performance is good, and the durability is high.
[0057]
【The invention's effect】
According to the present invention, sub fuel injection can be performed with an appropriate setting, and at the same time, lubrication of the cylinder wall surface can be ensured by evaporating the sub injected fuel.
[0058]
Moreover, if it comprises so that the injection control in an oil injection part may be performed with a solenoid valve, control can be performed at high speed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of an internal combustion engine of the present invention.
FIG. 2 is a diagram schematically showing the structure of a cylinder of an internal combustion engine according to the present invention.
FIG. 3 is a block diagram showing an oil path of the internal combustion engine.
FIG. 4 is a perspective view showing an oil path of the internal combustion engine.
FIG. 5 is a flowchart showing operations of post injection and cooling oil injection of the internal combustion engine.
FIG. 6 is a graph showing a relationship between a full load characteristic of an internal combustion engine and a post fuel injection region.
[Explanation of symbols]
1 Cylinder 2 Fuel Injection Valve 3 Piston 4 Oil Injection Unit 5 Control Unit 6 Solenoid Valve

Claims (3)

A fuel injection valve for injecting fuel into the cylinder;
An oil jet device that performs oil injection for cooling toward at least one of the piston or the cylinder,
In the internal combustion engine capable of sub fuel injection executed during main fuel injection and expansion stroke, exhaust stroke to the fuel injection valve,
An internal combustion engine that prohibits oil injection by the oil jet device when executing the sub fuel injection. A fuel injection valve for injecting fuel into the cylinder;
An oil jet device that performs oil injection for cooling toward at least one of the piston or the cylinder;
An injection control unit that controls the operation and stop of the oil injection unit, while causing the fuel injection valve to perform main fuel injection and expansion stroke, and auxiliary fuel injection that is executed during the exhaust stroke,
2. The internal combustion engine according to claim 1, wherein the injection control unit stops oil injection in the oil injection unit for a predetermined time in synchronization with a sub fuel injection timing. 3. The internal combustion engine according to claim 1, wherein the oil injection unit includes an electromagnetic valve, and the oil injection is controlled by intermittently energizing the electromagnetic valve. 4.

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