JPH0756217B2 - Fuel injection timing controller for swirl chamber type diesel engine - Google Patents

Description

TECHNICAL FIELD The present invention controls the timing of fuel injection to a combustion chamber of a diesel engine equipped with a sub-combustion chamber called a swirl chamber according to the operating state of the engine. The present invention relates to a fuel injection timing control device for a swirl chamber type diesel engine.

(Prior Art) As a measure for purifying exhaust gas of an automobile equipped with a diesel engine, reduction of NOx components, HC components, CO components and fine particles usually called particulates in exhaust gas can be mentioned. And to reduce the NOx component of these,
It is known as an effective countermeasure to reduce the combustion temperature by delaying the timing of injecting fuel into the combustion chamber of the engine, performing injection timing control for keeping the fuel injection timing in a retarded state.

On the other hand, setting the fuel injection timing in the retarded state tends to reduce the combustibility in the combustion chamber, which is disadvantageous in terms of engine output characteristics and fuel consumption, and in particular, a sufficient engine output is required. When the engine is in the medium to high load operation range, there is a possibility that the engine output may be insufficient. Therefore, as the engine shifts from the low load operating range to the medium to high load operating range, control is performed to switch the fuel injection timing to an advanced state that advances the fuel injection timing. For example, it is described in Japanese Utility Model Laid-Open No. 58-132141. As described above, the fuel injection timing is switched from the retarded state to the advanced state before the load state of the engine reaches 3/4 of the full load, and the improvement of the engine output characteristic is prioritized.

By the way, in such a diesel engine, in addition to the main combustion chamber formed in relation to the cylinder portion, a swirl chamber as a sub-combustion chamber is provided above or to the side of the main combustion chamber to provide compressed air. A swirl chamber type diesel engine that creates a swirl in the swirl chamber to improve the mixing state of compressed air and fuel, resulting in higher average effective pressure to increase engine output and fuel consumption rate. The engine is well known. And further,
In order to further improve the combustion characteristics in such a swirl chamber type diesel engine, the swirl chamber is formed of a chamber member using a heat insulating material such as ceramic so as to have a heat insulating structure for the cylinder head. Is proposed.

In a swirl chamber type diesel engine having a swirl chamber having a heat insulating structure such as formed of a chamber member using a heat insulating material such as ceramic, the swirl chamber is increased as a result of increasing the combustion temperature and the combustion speed. It has been found that the engine output is increased and the above-mentioned particulates are reduced as compared with a swirl chamber type diesel engine having a peripheral wall made of steel or cast iron. However, on the other hand, in a swirl chamber type diesel engine having a swirl chamber having an adiabatic structure, the NOx component in the exhaust gas tends to increase due to the higher combustion temperature. In order to suppress the increase, the injection timing control that puts the above-mentioned fuel injection timing into the retarded state will be performed, but in that case, depending on the conventional fuel injection timing control mode, NOx cannot be effectively reduced. Therefore, there is a possibility that the characteristic that a high output can be obtained is not effectively used and that the effect of reducing the particulates may be impaired.

(Object of the Invention) In view of such a point, the present invention provides a swirl chamber having a heat insulating structure with respect to a cylinder head by taking measures such as being formed of a chamber member using a heat insulating material such as ceramic. In the equipped swirl chamber type diesel engine, the fuel injection timing by the fuel injection means is adjusted according to the operating state of the engine, and the advance angle control is performed in a specific manner by effectively utilizing the characteristic that a high output is obtained. As a result, NOx components and particulates in the exhaust gas can be effectively reduced,
Another object of the present invention is to provide a fuel injection timing control device for a swirl chamber type diesel engine, which is designed to obtain a sufficiently high output when the engine is in a high load operation range.

(Structure of the Invention) A fuel injection timing control device for a swirl chamber type diesel engine according to the present invention uses a swirl chamber type diesel engine in which a swirl chamber communicating with a main combustion chamber is formed with a heat insulating structure for a cylinder head. Fuel injection means for injecting the fuel through the swirl chamber, and injection timing control means for adjusting the fuel injection timing by the fuel injection means in accordance with the operating state of the engine. The injection timing is set to a relatively slow first timing when the engine load is within a range of at least less than 4/5 of the full load in the low load range, the medium load range, and the high load range, and the swirling flow Room type diesel engine load is 4/5 of full load
Within the above range, the advance angle control is performed to switch from the first time period to the second time period which is earlier than the first time period by a predetermined advance angle amount.

By doing so, the desired engine output can be obtained over the full load operating range of the engine, and in particular, when the engine is in the high load operating range, it is possible to obtain a sufficiently high output, and at the same time, the engine can be operated at medium or high. It is possible to effectively reduce NOx components and particulates in the exhaust gas up to the load operation range at the same time.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of a fuel injection timing control device for a swirl chamber type diesel engine according to the present invention together with a diesel engine to which it is applied. In FIG. 1, the diesel engine 1 is, for example, an in-line 4-cylinder type swirl chamber type, and a branch portion of an intake passage 4 and an exhaust passage 5 is connected to each of the four combustion chambers 2. . As shown in FIG. 2, each combustion chamber 2 includes a main combustion chamber 11 surrounded by a cylinder block 6, a cylinder head 7, a piston 8, an intake valve 9 and an exhaust valve (not shown).
And a swirl chamber (sub-combustion chamber) 13 communicating with the main combustion chamber 11 through a nozzle hole 12, and the temperature Ts of the cooling water related to the temperature state of the combustion chamber 2 is attached to the cylinder block 6. The detected water temperature sensor SS. On the peripheral wall of the swirl chamber 13, a ceramic chamber member 14 which is fitted into the cavity provided in the cylinder head 7 through a metal reinforcing ring 10 is used. 7 has a heat insulating structure, which increases the temperature in the swirl chamber 13 as compared with the case of a swirl chamber type diesel engine in which the chamber member forming the swirl chamber is made of steel or cast iron. It is designed to be faster. In the swirl chamber 13, a glow plug 16 mounted on the cylinder head 7 for preheating and warming up is provided.
Of the fuel injection nozzle 17 and the injection port 14a formed in the chamber member 14 of the swirl chamber 13
It is designed to face. The fuel injection nozzle 17 is configured to inject a predetermined amount of fuel, which is pumped from the fuel injection pump 18 in each intake stroke, according to the operating state of the diesel engine 1 into the swirl chamber 13 in the compression stroke.

The fuel injection pump 18 is, for example, an electronically controlled distribution type injection pump, and has a drive shaft 19 that is rotated by the crankshaft of the diesel engine 1 and rotates in synchronization with the diesel engine 1. A rotation speed sensor NS that detects the rotation speed of the rotating body that is correlated with the rotation speed of the drive shaft 19 is arranged at a predetermined position. Further, the fuel injection pump 18 is provided with a governor device 20 for adjusting the amount of fuel to be pressure-fed to the fuel injection nozzle 17 in a predetermined manner. Further, the fuel injection pump 18 has an electronic timer 23 as a fuel injection timing adjusting means for controlling the injection timing of the fuel injected from the fuel injection nozzle 17 into the swirl chamber 13.
Is built in. The operation of the electronic timer 23 is controlled by the injection timing control valve 25. Further, an accelerator sensor AS adapted to detect the accelerator pedal depression amount Accp corresponding to the engine load Le is installed on the lever portion of the accelerator pedal 21.

The intake air introduced into the combustion chamber 2 through the intake passage 4 flows into the swirl chamber 13 during the compression stroke to form a swirl, and the fuel injected from the fuel injection nozzle 17 is mixed and burned, and then exhausted. The exhaust gas becomes a gas and is discharged to the exhaust passage 5. However, a part of the exhaust gas is exhaust gas whose both ends are connected to the intake passage 4 and the exhaust passage 5 due to the negative pressure difference between the intake passage 4 and the exhaust passage 5. It is returned to the intake passage 4 through the return passage 30 and is recirculated. An exhaust gas recirculation control valve 31 is provided in the middle of the exhaust gas recirculation passage 30. The exhaust gas recirculation control valve 31 has a lift for detecting the lift amount of the valve element 32 and thus the effective opening area of the exhaust gas recirculation port 33. The sensor RS is arranged. The negative pressure source side of the conduit 35 for introducing negative pressure into the negative pressure introducing chamber 34 of the exhaust gas recirculation control valve 31 is connected to the negative pressure supply port 37 of the negative pressure control valve 36, and the vacuum of the negative pressure control valve 36 is also reduced. The port 38 is connected, for example, via a conduit 40 to a vacuum pump 39 that is rotationally driven by a crankshaft (not shown) of the diesel engine 1. Further, the negative pressure control valve 36 has an atmosphere suction port 41 that communicates with the atmosphere.

In order to control the operation of each part configured as described above,
A control unit 100 with a built-in timer is provided,
The control unit 100 includes a detection signal Ss corresponding to the temperature Ts of the cooling water corresponding to the temperature of the diesel engine 1 from the water temperature sensor SS, and a detection signal Sn corresponding to the rotation speed of the diesel engine 1 from the rotation speed sensor NS. And the accelerator sensor AS
From the accelerator pedal Accp, the detection signal Sa corresponding to the engine load Le, and the effective opening area of the exhaust gas recirculation port 33 from the lift sensor RS, and thus the detection signal Sr corresponding to the exhaust gas recirculation amount. , Respectively, and the detection signal Sb corresponding to the change of the primary voltage from the battery BS and the detection signal corresponding to the atmospheric pressure from the atmospheric pressure sensor DS.
Sd etc. is input.

Then, the control unit 100, the various detection signals Ss, described above,
Based on Sn, Sa, Sr, Sb, Sd, etc., an injection timing control signal Ct for controlling the fuel injection timing of the diesel engine 1 is sent to the injection timing control valve 25, and an exhaust gas recirculation control for controlling the exhaust gas recirculation amount. The signal Ce is supplied to the negative pressure control valve 36, and the glow register provided in the glow plug 16 and the intake passage 4.
The heating control voltage Cg for heating 59 is delivered.

Under the control of the control signals Ce and Ct and the control unit 100 that sends out the control voltage Cg as described above, the fuel injection timing control in the example of the fuel injection timing control device for the swirl chamber type diesel engine according to the present invention is performed. Is performed as described below.

The injection timing control signal Ct sent from the control unit 100 to the injection timing control valve 25 is a pulse signal having a pulse width t ₁ corresponding to the amount of advance angle to be taken, whereby the injection timing The control valve 25 is energized and excited every unit cycle t with the pulse width t ₁ of the injection timing control signal Ct which is changed according to the operating state of the engine to be opened. Therefore, when the fuel injection timing is controlled by the injection timing control signal Ct, the injection timing control signal Ct
Advance amount of the fuel injection timing is controlled by the duty time ratio corresponding to (t ₁ / t), the advance amount of the more fuel injection timing injection timing control signal Ct duty (t ₁ / t) is a small Is considered to be large. Further, the pulse signal of the exhaust gas recirculation control signal Ce sent from the control unit 100 to the negative pressure control valve 36 also has a pulse width t ₂ corresponding to the exhaust gas recirculation ratio (EGR ratio) to be taken, and every unit cycle t ₀ The negative pressure control valve 36 is energized and excited to open the EGR passage at a pulse width t ₂ of, and the larger the duty (t ₂ / t ₀ ) of Ce, the larger the EGR rate.

Next, as described above, in relation to the exhaust gas recirculation control in the swirl chamber type diesel engine 1 in which the ceramic chamber member 14 having excellent heat insulating properties is used on the peripheral wall of the swirl chamber 13, The matters clarified by experiments by the inventor of the present application will be described with reference to FIGS.

3 to 5 show experimental results D obtained for the heat insulation type diesel engine 1, in which the peripheral wall of the swirl chamber is formed by using, for example, a steel chamber member, and a heat insulation structure is taken. No ordinary swirl chamber type diesel engine (hereinafter referred to as normal type engine)
It is shown in comparison with the result F obtained for.

Figures 3, 4, and 5 show the exhaust when the engine average effective pressure Pe is 1 (kg / cm ² ), 3 (kg / cm ² ), and 5 (kg / cm ² ), respectively. Change the reflux rate (EGR rate) E,
In addition, the amount of NOx component and the amount of particulate measured by changing the advance amount that determines the fuel injection timing are
The horizontal axis represents the Ox component amount NOx and the vertical axis represents the particulate amount Par. In each figure, the broken line shows the same EGR rate line, and the solid line Adv shows the horizontal line as shown in FIG. Taking the engine speed Ne on the axis and the accelerator pedal depression amount Accp corresponding to the engine load on the vertical axis, the advance amount map showing the advance amount θ and the engine speed Ne and accelerator pedal in each situation are shown. It corresponds to a state in which the fuel injection timing is advanced by the advance amount obtained by collating with the depression amount Accp (hereinafter, referred to as advance angle state A), and the solid line Ret indicates a constant retard angle from the above advance angle state. The amount, here, corresponds to a state in which the fuel injection timing is delayed by 6 degrees (hereinafter referred to as a retarded state R).

The swirl chamber type diesel engine in this experiment has an average effective pressure Pe of about 7.5 (kg / cm ² ) at full load.

And from the result of FIG. 3, when the average effective pressure Pe is 1,
Therefore, when the engine is in the low load operation range, the amount of particulates in the exhaust gas in the diesel engine 1 (D) is higher than that in the normal type engine (F) under each condition. It can be seen that when the EGR rate E of the diesel engine 1 is about 40 to 60%, the amount of NOx components contained in the exhaust gas is suppressed to the same level as in the normal type engine.

Therefore, the diesel engine 1 has an average effective pressure Pe of 1
In the case of, the EGR rate E is set to about 60%, but when the EGR rate E is about 60%, the retarded state R
It can be seen that both of the amount of particulates and the amount of NOx components in the exhaust gas are smaller when T is taken than when the advanced angle state A is taken.

In this case, also in the case of a normal type engine, similarly, the amount of particulates and the amount of NOx components in the exhaust gas when the engine is in the retarded state R is more than when it is in the advanced state A. It can be seen that

Further, from the result of FIG. 4, when the average effective pressure Pe is 3, therefore, when the engine is in the medium load operation range, when the EGR rate E of the diesel engine 1 is about 20 to 60%,
Normal type with the amount of particulates in the exhaust gas
It is smaller than in the case of the engine, and when the EGR rate E of the diesel engine 1 is about 40 to 60%, the amount of NOx components in the exhaust gas is suppressed to the same level as in the case of the normal type engine. .

Therefore, the diesel engine 1 has an average effective pressure Pe of 3
In the case of, the EGR rate E is set to about 40%, but when the EGR rate E is about 40%, the amount of NOx components in the exhaust gas when the retarded state R is taken. The same is true when the advanced angle state A is taken, but the amount of particulates in the exhaust gas is far greater when the retarded angle state R is taken than when the advanced angle state A is taken. You can see that it will decrease.

In this case, also in the case of the normal type engine, when the retarded angle state R is set, the amount of NOx components in the exhaust gas is slightly smaller than when it is in the advanced angle state A. The amount of is greatly reduced.

Further, from the result of FIG. 5, similarly, the average effective pressure Pe
When the engine is in a relatively high load operation range, the amount of particulates in the exhaust gas is
Under each condition, the diesel engine 1 has a significantly smaller amount than the normal type engine, and the EGR rate E of the diesel engine 1 is about 1
It can be seen that when it is 0 to 20% or more, the amount of NOx components in the exhaust gas is suppressed to the same extent as in the case of a normal type engine.

Therefore, the diesel engine 1 has an average effective pressure Pe of 5
In the case of, the EGR rate E is set to about 20% and the operation is performed, but when the EGR rate E is about 20%, the retarded state R
It can be seen that both of the amount of particulates and the amount of NOx components in the exhaust gas are significantly reduced when is taken as compared to when the advanced state A is taken.

If the average effective pressure Pe is 5, normal type
The engine is usually operated with the EGR rate E set to zero,
In such a case, it can be seen that when the advance angle state A is set, the NOx component in the exhaust gas is reduced, but the particulate matter is increased, as compared with when the retard angle state R is set.

From these experimental results, the diesel engine 1 in which the swirl chamber 13 is insulated is irrespective of the load state from the viewpoint of reducing the amount of NOx components and the amount of particulates in the exhaust gas. It would be desirable to be in the retarded state R. Further, in the diesel engine 1, since the swirl chamber 13 is insulated and the combustion temperature is raised and has high output characteristics, the average effective pressure Pe becomes about 5 to 6 from the low load operation range. The desired engine output can be obtained even if the retarded state R is taken up to the operating range at a relatively high load. However, the engine load becomes even higher, and the average effective pressure Pe becomes 6 or more.
In an operating range with a high load of 5 or more, a sufficiently high engine output is required, so it is desirable to prioritize the engine output characteristics and set the advance angle state A.

On the other hand, in the normal type engine, the retarded state R is taken in the low and medium load operation range, and for example, the average effective pressure Pe is
In the medium and high load operation range where is 5 or more, the advance angle state A is taken.

Based on the above experimental results and the discussions based on them,
In the fuel injection timing control device for a swirl chamber type diesel engine according to the present invention as shown in the figure, the fuel injection timing for the diesel engine 1 having the insulated swirl chamber 13 is shown in FIG. The load of the diesel engine 1 as shown by the load Le being taken is the full load.
Within the range of 4/5 or more, the timing corresponding to the retarded state R is switched to the timing corresponding to the advanced state A, and the load of the diesel engine 1E is changed to the low load region, the medium load region and the high load region. In the range from the timing corresponding to the retarded state R, which is less than 4/5 of the full load, to the load state where the timing is switched to the advanced angle state A, the retarded state is continuously maintained. It is assumed that the time corresponding to R is taken. FIG. 7 also shows the state of fuel injection timing in the normal type engine with a broken line. In the case of the normal type engine, the retarded state R is within the range of 3/4 or less of the full load.
Is switched from the time corresponding to A to the time corresponding to the advanced angle state A.

Then, the fuel injection timing in the diesel engine 1 is within the range in which the load of the diesel engine 1 is 4/5 or more of the full load, from the timing corresponding to the retarded state R to the advanced state A
In order to perform the fuel injection timing control so that the timing can be switched to the timing corresponding to, the control unit 100, based on the detection signals Ss, Sn, Sa, Sr, etc. from the respective sensors, advances as shown in FIG. An injection having a pulse width t ₁ required to obtain a fuel injection timing corresponding to the advance amount determined from the advance amount map and the advance amount map that obtains the advance characteristic as shown in FIG. 7. When the timing control signal Ct is supplied to the injection timing control valve 25 and, for example, the load which is slightly larger than 4/5 of the full load is not reached, the fuel injection determined by the advance amount shown in FIG. When the timing is delayed by 6 degrees and the load of the diesel engine 1 becomes a load slightly larger than 4/5 of the full load, the fuel injection timing determined by the advance amount shown in FIG. 6 is set. It works so that it does not change.

Although the electronically controlled distribution type injection pump is used in the swirl chamber type diesel engine 1 to which the above-mentioned example is applied, a mechanical distribution type injection pump may be used, and the advance angle at a load of 4/5 or more may be used. To switch from the retard angle to the retard angle, the port (fuel pressure relief port) position of the governor sleeve of the load timer may be adjusted. Further, in the structure of the swirl chamber, the swirl chamber 13 is formed by the chamber member 14 using ceramic which is a heat insulating material to provide a heat insulating structure for the cylinder head. May be made of a non-heat insulating material, and a heat insulating portion may be provided between the outer periphery of the chamber member and the cylinder head so that a heat insulating structure can be obtained.

(Effects of the Invention) As is apparent from the above description, according to the fuel injection timing control device for a swirl chamber type diesel engine of the present invention, for example,
The fuel injection timing in a swirl chamber type diesel engine having a swirl chamber formed of a heat insulating material such as ceramics and having a heat insulating structure for the cylinder head is set to the load state of the engine and the operating state thereof. When the load of the swirl chamber type diesel engine is within the range of at least less than 4/5 of the full load among the low load range, the medium load range and the high load range, the fuel injection timing is relatively adjusted. If the first timing is late, and the load of the swirl chamber type diesel engine is 4/5 or more of the full load, the fuel injection timing is advanced from the first timing by a predetermined advance amount. By performing advance control to switch to the timing, it is possible to obtain a sufficiently high output, especially in the high load operating range, without impairing the operating performance of the engine, and to improve the performance of the exhaust gas. Both Ikyureto and NOx components can be allowed to effectively reduce. Therefore, the fuel injection timing control device for a swirl chamber type diesel engine according to the present invention provides a swirl chamber type diesel engine having a swirl chamber with a heat insulating structure for the cylinder head, and a high output and exhaust gas. It is possible to reduce the NOx component in the exhaust gas by taking advantage of the characteristic that the particulates contained therein are reduced, which is a major contribution to the exhaust gas purification.

[Brief description of drawings]

1 is a schematic configuration diagram showing an example of a fuel injection timing control device for a swirl chamber type diesel engine according to the present invention together with a diesel engine to which it is applied, and FIG. 2 is a swirl chamber type diesel engine shown in FIG. FIG. 3 to FIG. 5 are partial cross-sectional views of the main body of FIG. 1, which show experimental results used to explain an example of a fuel injection timing control device for a swirl chamber type diesel engine according to the present invention shown in FIG. FIG. 6 is a characteristic diagram showing the advance amount characteristic used to obtain the experimental results shown in FIGS. 3 to 5, and FIG. 7 is a characteristic used to explain the operation of the example shown in FIG. It is a figure. In the figure, 1 is a swirl chamber type diesel engine, 2 is a combustion chamber,
4 is an intake passage, 5 is an exhaust passage, 7 is a cylinder head, 13
Is a swirl chamber, 14 is a chamber member, 18 is a fuel injection pump, 20
Is a governor device, 25 is an injection timing control valve, 30 is an exhaust gas recirculation passage, 31 is an exhaust gas recirculation control valve, 36 is a negative pressure control valve,
100 is a control unit, AS is an accelerator sensor, NS is a rotation speed sensor, and RS is a lift sensor.

Claims (1)

[Claims] 1. A fuel injection means for injecting fuel through the swirl chamber in a swirl chamber type diesel engine in which a swirl chamber communicating with a main combustion chamber has a heat insulating structure for a cylinder head, and the fuel injection means. The fuel injection timing is adjusted according to the operating state of the swirl chamber type diesel engine, and the load of the swirl chamber type diesel engine is at least the full load in the low load region, the medium load region and the high load region.
When the fuel injection timing is within the range of less than 4/5, the fuel injection timing is set to the relatively late first time, and the fuel injection is performed within the range where the load of the swirl chamber type diesel engine is 4/5 or more of the total load. A swirl chamber type diesel engine configured to include injection timing control means for performing advance control for switching the timing from the first timing to a second timing that is earlier than the first timing by a predetermined advance amount. Fuel injection timing control device.