JPH0996241A - Combustion device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel consumption while generation of black smoke and NOx is suppressed, by protruding a protrusion in almost the center of a bottom surface in a combustion chamber hollowly provided in a piston top surface, injecting fuel toward this protrusion, also controlling the fuel so as to be pilot injected before a prescribed time of main injection. SOLUTION: A cavity 901 in a top surface of a piston 9 in a Diesel engine is hollowly provided, a collision member 902 is protrusively provided in a bottom part center of this cavity. A fuel injection valve 10 supported to a cylinder head 801 is arranged so that a jet 12 of a nozzle 16 is opposed to a just above side of the collision member 902 relating to its collision wall 903. When the engine is operated, fuel of an accumulator 36 is atomizingly injected in a combustion chamber C by turning on a first three-way solenoid valve 34, two times repetition of this atomization performs pilot/main injection, but here, so as to start the pilot injection 3msec or more before start timing of the main injection, the three-way solenoid valve 34 is switch controlled by an ECU66.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for a diesel engine which adopts a collision diffusion combustion system, and more particularly, when a fuel injection system adopts a pressure accumulation system, injection timing, injection pressure and injection in the entire operating range of the diesel engine. The present invention relates to a combustion device for a diesel engine, the amount of which can be changed and pilot injection can be performed.

[0002]

2. Description of the Related Art Diesel engines have direct combustion (DI), pre-combustion chamber and swirl chamber (IDI) combustion systems.
The direct injection diesel engine has good fuel efficiency, but a rapid increase in heat generation rate due to a rapid combustion due to ignition delay raises the noise level and causes a rapid increase in NO _X due to an increase in combustion temperature. Invite. On the other hand, in a pre-combustion chamber type or swirl chamber (IDI) diesel engine, fuel is pre-combusted in the pre-combustion chamber or swirl chamber, and then main combustion is performed in the main combustion chamber. The rate is held relatively low and NOx generation is low, but heat loss and pump loss are large and fuel consumption is relatively low.

An example of a combustion system of a direct injection (DI) diesel engine is a collision diffusion combustion system. For example, in Japanese Unexamined Patent Publication No. 59-79031, a protrusion is formed in a combustion chamber composed of a cavity formed in the top face of a piston, and fuel is directly injected from the injection nozzle to collide and diffuse fuel particles. A technique for promoting combustion by this is disclosed. Further, in the collision-diffusion combustion type as shown in FIGS. 20 (a) and 20 (b), a cavity 2 is recessed on the top surface of a piston 1 of a diesel engine, and a cylinder head 3 is formed.
An injection nozzle 5 is provided on the cylinder facing wall 4. Particularly, the cylinder facing wall 4 is equipped with a collision member 7 having a mounting portion 6 fixed near the injection nozzle 5 so as to hang down. In this case, regardless of the position of the piston, the fuel spray from the injection nozzle 5 collides with the collision member 7 at a fixed position to collide and diffuse,
It mixes with air in the cavity 2 and proceeds to the combustion stroke. By the way, the direct injection (DI) diesel engine, which has relatively good fuel consumption, is required to reduce NO _X and noise in particular, and the pilot injection method is effective as one of the solutions, and its improvement is proceeding. Has been.

Conventionally, when performing pilot injection in a direct injection (DI) diesel engine, as shown in FIGS. 18 (a) and 18 (b), the combustion chamber C is compared by a fuel injection valve I near the crank angle TDC. A pilot injection of a small amount of fuel is performed, and then, as shown in FIGS. 19 (a) and 19 (b),
A relatively large amount of fuel is injected. In this case, the swirl S is generated in the combustion chamber C by the action of the intake system, the pilot-injected fuel spray f1 burns, and the flame thereof receives the action of the swirl S in the combustion chamber C, and the swirl S is generated as shown in FIG. a),
As indicated by reference sign f1 ′ in (b), the position is displaced in the swirl S direction, and the main injected fuel spray f2 is mixed there, and the pilot flame f1 ′ that has been ignited and burned earlier or has already burned. The burned gas will be introduced into the main fuel injection f2. Therefore, the introduction of new air into the spray is suppressed and black smoke increases.

On the other hand, it is quite difficult in practice to use a collision-diffusion combustion type diesel engine, which is an example of a direct injection type, but if pilot injection can be performed, then FIG.
0 (a), (b), pilot injection is performed in the combustion chamber 2 by the fuel injection valve 5 in the vicinity of TDC, and then, as shown in FIGS. 21 (a), (b), main injection is performed. Is done. In this case, the pilot sprayed fuel spray f3
Is diffused into the combustion chamber 2 and burned, but the fuel spray f4 is main-injected by chasing it, and the flame of the pilot fuel spray f3 which is ignited and burned first suppresses the combustion promotion of this fuel spray f4. .

[0006]

Problems to be Solved by the Invention FIGS. 19 (a) and 19 (b)
As shown in FIG. 3, in the case of a direct injection (DI) diesel engine, the flame of the pilot fuel spray f3 is surrounded by the main sprayed fuel spray f2, so that mixing of the main injected fuel with air becomes poor, which causes graphite generation. Made of On the other hand, FIG.
As shown in FIGS. 1 (a) and 1 (b), in the diesel engine of the collision diffusion combustion system, the flame of the pilot spray f3 is pushed into the inner peripheral wall surface side of the combustion chamber by the main sprayed fuel spray f4, resulting in poor mixing. And is a cause of graphite generation.

As described above, not only the normal direct injection type diesel engine but also the collision diffusion combustion type diesel engine having good fuel diffusibility in the combustion chamber is used, and the pilot injection type is applied to the diesel engine so that the fuel consumption is comparatively low. However, in order to obtain a collision diffusion combustion type diesel engine capable of reducing NO _x and noise, there is a problem of black smoke generation, and improvement thereof is desired. An object of the present invention is to suppress the black smoke generation, fuel consumption is good, a reduction in NO _X, is to provide a diesel engine of a collision diffusion combustion system attained a reduction in noise.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 is such that a combustion chamber recessed in a piston top surface of a diesel engine and a bulge at approximately the center of the bottom surface of the combustion chamber. And a fuel injection valve having a fuel injection projection that is arranged so as to make fuel collide with the fuel injection projection, and the injection timing, injection pressure, and injection amount of the fuel injected from the fuel injection valve. And a fuel supply control means for controlling the fuel injection control means, wherein the fuel supply control means performs the pilot injection before a predetermined time of the main injection timing.

According to a second aspect of the present invention, in the diesel engine combustion apparatus according to the first aspect, a supply pump whose supply amount and injection pressure can be varied by controlling a solenoid energization time, and the supply pump supplies the same. The fuel storage device is provided with a pressure accumulating chamber for temporarily storing fuel, and fuel supply means having a three-way solenoid valve for switching the fuel from the pressure accumulating chamber to injection or non-injection. It is characterized in that pilot injection and main injection are performed by switching and controlling the one-way solenoid valve.

According to a third aspect of the present invention, in the diesel engine combustion apparatus according to the second aspect, the fuel supply control means is configured to start the pilot injection at least 3 msec before the main injection start timing. It is characterized in that the three-way solenoid valve is switched and controlled.

According to a fourth aspect of the present invention, in the diesel engine combustion apparatus according to the first aspect, the injection hole of the fuel injection valve is directed vertically downward toward the projection, and the length of the injection hole is long. It is characterized by being larger than three times the diameter of the injection hole.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The fuel injection control device for a diesel engine of FIG. 1 is installed in an in-line multi-cylinder diesel engine (hereinafter simply referred to as engine) 8. The first cylinder will be mainly described here because each cylinder has the same configuration. Fuel is injected into a combustion chamber C of the engine 8 from an injection port 12 of a fuel injection valve 10, and the fuel injection valve 10 is supplied to a fuel supply unit A and an engine control unit (hereinafter simply referred to as ECU) 66 as a fuel supply control unit. Connected.

The engine 8 has a combustion chamber C for each cylinder.
The combustion chamber C is formed by a cylinder block (not shown), a cylinder head 801, and a piston 9 that slides in the cylinder block. A cavity 901 is provided in the top surface of the piston 9 as a recess. This cavity 9
A collision member 902 is provided at the center of the bottom of 01, and a collision wall 903 forming the top surface of the collision member is formed lower than the piston top surface by a predetermined amount h, whereby the engine top dead center (T
Even when it is located below the position near DC), the collision fuel spray is suppressed from scattering in the gap t between the piston top surface and the cylinder facing wall of the cylinder head. The collision wall 903 can be made of ceramic or the like in consideration of heat resistance and wear resistance.

The injection port 12 of the nozzle 16 in the fuel injection valve 10 supported by the cylinder head 801 of this engine is arranged immediately above the collision wall 903. Here, if the dispersion characteristic of the fuel spray that collides and scatters from the collision wall 903 changes according to the distance between the injection port 12 of the nozzle 16 and the collision wall 903 or the fuel injection pressure, the mixed evaporation with air changes, and the combustion also changes. Be regarded. Therefore, in the collision combustion method, in order to optimize combustion, it is necessary to apply an injection device that can independently control the injection timing and the injection pressure, such as increasing the injection pressure when the interval is long and decreasing the pressure when the interval is short. . The fuel injection valve 10 connected to the fuel supply means A includes a nozzle holder 20 supported by the cylinder head 801, and the nozzle 16 is integrally supported at the lower end of the nozzle holder 20. A nozzle needle 18 capable of connecting and disconnecting the fuel reservoir 14 and the injection port 12 is slidably accommodated in the nozzle 16.

The injection port 12 is a single port and is formed so as to be directed vertically downward toward the collision wall 903. Here, as shown in FIG. 6, the length 1 of the injection port 12 is set to be larger than three times the injection hole diameter d. In setting l / d ≧ 3, the following characteristics were taken into consideration. That is,
As shown in FIG. 7, the injection pressure was maintained at 150 MPa, and the spray angle θ ° at a position at a distance of 70 mm from the nozzle was 1
The length 1 of 2 and the injection hole diameter d were changed, and the ratio was sequentially measured. As a result, when the spray angle θ ° was 1 / d ≧ 3, the spray angle was sufficiently narrowed, and a relatively fine spray was obtained. Moreover, as shown in FIG. 8, when looking at the flow rate distribution of the spray, 1 / d = 1
Compared with the case of, the flow rate distribution was sufficiently narrowed when 1 / d = 3, which proved to be suitable for the collision diffusion method. Note that FIG.
Shows a diagram in which the deviation of the deviation angle in the injection direction when the injection port is 1 / d = 2.0 and when the injection port is 1 / d = 3.8 is plotted along the number of measurements. Here again, the nozzle has a l / d = 3.
In the case of 8, the deviation of the deviation angle becomes extremely smaller than that in the case of 1 / d = 2.0, and it is clear that the injection direction is stable.

The nozzle needle 18 of the fuel injection valve 10 is pressed in the valve closing direction by the hydraulic pressure (fuel pressure) applied to the oil chamber 26 above the command piston 28 via the push rod 22 housed in the nozzle holder 20. . Nozzle holder 2
A hydraulic piston 28 is slidably fitted in the oil chamber 26 inside the valve. The outlet b of the first three-way solenoid valve 34 is connected to the upper end of the oil chamber 26 via a one-way valve 30 and an orifice 32 which are arranged in parallel with each other. First three-way solenoid valve 34
It has an inlet a communicating with the storage vessel 36 and a second outlet c communicating with the fuel tank 38. The inlet a is selectively connected to the first outlet b or the second outlet c by a valve body 42 driven by the electromagnetic actuator 40. The inlet a communicates with the first outlet b when the electromagnetic actuator is off, and the inlet a when the electromagnetic actuator is on. b is configured to communicate with the second outlet c. A feed hole 44 is provided in the nozzle holder 20 and the nozzle 16 to connect the fuel reservoir 14 to the accumulator 36.

A high-pressure fuel supply pump 46 is connected to the accumulator 36, and the pump has a plunger 50 reciprocated by a cam 48 which is driven in conjunction with a crank shaft (not shown) of the engine 8. A fuel tank 38 is connected to a pump chamber 54 in which the plunger 50 is inserted via a low-pressure feed pump 52, and when the plunger 50 is driven, the fuel supplied from the feed pump 52 is pressurized in the pump chamber 54, and the fuel is supplied in one direction. The pressure is fed to the pressure storage device 36 via the valve 56.

A spill valve 64 as a first electromagnetic valve driven by an electromagnetic actuator 62 is interposed between a discharge side passage 58 of the pump chamber 54 and a suction side passage 60 communicating with the feed pump 52. The electromagnetic actuator 62 and the electromagnetic actuator 40 are respectively connected to the ECU 66, and in particular, by controlling the opening / closing of the spill valve 64 serving as the first electromagnetic valve, the fuel hydraulic pressure stored in the accumulator 36 is reduced to the first to the third described later. The pressure can be adjusted to correspond to the operating conditions of. Although FIG. 1 shows the fuel injection valve 10 of the first cylinder and its fuel supply system, the other cylinders are also provided with the fuel injection valve and the fuel supply means A of the same structure, and their respective electromagnetic actuators are also provided. It is connected to the ECU 66.

The ECU 66 includes a cylinder discriminating device 68 for discriminating individual cylinders of a multi-cylinder engine, an engine speed and crank angle detecting device 70, an engine load detecting device 72, and a fuel pressure sensor for detecting the fuel pressure inside the accumulator 36. 74 and, if necessary, auxiliary information such as temperature Ta, atmospheric pressure Pa, fuel temperature Tf, etc., which influences the operating condition of the engine, is fetched from the atmospheric temperature sensor 80, atmospheric pressure sensor 81, fuel temperature sensor 82, etc. Actuator 40, 6
Control 2 Here, the ECU 66 controls the fuel injection valve 10
A fuel supply control means for controlling the injection timing T, the injection pressure and the injection amount Q of the fuel injected from
Pilot injection and main injection are performed by switching and controlling the first three-way solenoid valve 34 at the time of fuel injection. In particular, the first three-way solenoid valve 34 is switched and controlled so that the pilot injection is started 3 msec or more before the start timing of the main injection.

An unillustrated read only memory (ROM) of the ECU 66 has an injection map Mp for calculating the injection timing T, pilot injection interval Δθ, pilot injection amount q and main injection amount Q as shown in FIG. No injection pressure map is stored. This injection map Mp
Is, for example, three threshold values Ne along the engine speed Ne.
i, Ne1, Ne2, and three threshold values Lo (no load) according to the engine load L, and each control value is set for each of the nine areas partitioned by L1 and L2. An injection pressure map (not shown) is set so that the injection pressure p can be calculated as a predetermined set value depending on whether the engine load L is low load or high load. The regions of the injection map Mp and the injection pressure map (not shown) here are further finely divided according to the situation, and respective control values are set.

Here, the storage device 3 for always ensuring a predetermined pressure.
No. 6 fuel is supplied to the fuel injection valve 1 when the first three-way solenoid valve 34 is turned on.
An injection system is used which is capable of spraying into the combustion chamber C by 0 and repeating it twice to inject both pilot injection and main injection, and can set the interval freely. Therefore, as shown by the broken line in FIG. 5, compared with the conventional fuel injection system that is not the pressure accumulation type, as shown by the solid line, the timing and injection rate of the main injection and pilot injection can be freely set within the injection period. Moreover, in the case of the conventional fuel injection system that is not the pressure accumulation type, there is a problem that the injection pressure becomes lower in the low rotation speed range, the atomization characteristic of the fuel deteriorates at the low rotation speed, and the black smoke generation amount increases. Since the injection pressure can be set high irrespective of the rotation range in this device of the formula, the atomization characteristics of the fuel are good and the amount of black smoke generated can be suppressed.

On the other hand, in this device, the injection timing T is set for each operation range, but here, as shown in FIG. 5, when setting each injection timing, the injection start timings tp1, t1 are set.
In addition to the injection end timings tp2 and t2, the pilot injection period (tp1-tp2) and the main injection period (t1-t2), that is, the injection amount is also set. Furthermore, the interval between the pilot injection timing tp1 and the main injection timing t1 (Δθ in crank angle or time interval Δ
t) is set to be separated by at least 3 msec or more. Thus, after completing the combustion of fuel spray that is pilot injection, performs main injection, suppressing black smoke, reduced NO _X. Further, in order to reduce noise and improve fuel efficiency, optimum values in each driving range are experimentally selected.

Incidentally, an example of data used for setting the injection map Mp is shown in FIGS. However, this data is an example when the present fuel injection device is applied to a normal direct injection diesel engine and pilot injection is performed. That is, in FIG. 10, 20 at 1620 rpm
In-cylinder average temperature K ° C, heat release rate J / deg, in-cylinder pressure M during engine operation in the operating range E1 of% load (see FIG. 14)
The combustion characteristic diagram according to each crank angle change of Pa is shown. Here, the injection pipe pressure was 40 MPa, and the pilot injection amount was 3 mm ³ / st.

In the operating range E1 of 20% load at 1620 rpm, pilot injection is carried out from the main injection in Δθ1 = 34.0 deg at crank angle intervals and Δt = 3.5 at time intervals.
It was done 0msec earlier. In this case, in particular, in the heat release rate, for the non-pilot injection shown by the solid line, the broken line (Δθ1 = 34.0 deg) and the chain line (Δθ1 = 1)
The pilot injection shown by (5, 0 deg) is suppressed to a lower level, and the maximum in-cylinder pressure MPa is also indicated by a broken line (Δθ1 = 34.0 deg) and a chain line (Δθ1 = 15, 0 deg) with respect to the non-pilot injection shown by a solid line. The pilot injection shown is gentler, and NO _X and noise reduction can be expected.

FIG. 11 shows the crank angle changes of the cylinder average temperature K ° C., the heat release rate J / deg, and the cylinder pressure MPa during engine operation in the operating range E2 (see FIG. 14) at 1620 rpm and 40% load. A combustion characteristic diagram corresponding to is shown. Here, the injection pipe pressure is 40 MPa, and the pilot injection amount is 3 mm.
It was ³ / st. In the operating range E2 where the load is 40% at 1620 rpm, the pilot injection is more than the main injection at the crank angle interval Δθ2 = 34.0 deg, and at the time interval Δt =.
It was done earlier by 3.50 msec. In this case, the maximum in-cylinder pressure MPa was gentle with respect to the pilot injection. Moreover, in the heat release rate, the pilot injection indicated by the broken line (Δθ2 = 34.0 deg) and the chain line (Δθ2 = 15, 0 deg) is suppressed to be lower than the non-pilot injection indicated by the solid line, and NO _X and noise are also reduced. Can be expected to be reduced.

FIG. 12 shows the crank angle changes of the cylinder temperature K ° C., the heat release rate J / deg, and the cylinder pressure MPa during engine operation in the operating range E3 (see FIG. 14) at 1620 rpm and 80% load. A corresponding combustion characteristic diagram is shown. here,
Injection pipe pressure is 55 MPa, pilot injection amount is 3 mm ³ /
It was st. In the operating range E3 where the load is 80% at 1620 rpm, the pilot injection is carried out more than the main injection Δθ3 = 32.0 deg in the crank angle interval, and Δt = 3.
It took 29 msec earlier. In this case, in the heat release rate, the non-pilot injection shown by the solid line and the broken line (Δθ3 =
32.0 deg) and one-dot chain line (Δθ3 = 15, 0 deg)
There is no big difference with the pilot injection shown in g),
The non-pilot injection shown by the solid line is different from the pilot injection shown by the broken line and the chain-broken line only in that the in-cylinder temperature rises faster and the in-cylinder pressure increases more. For this reason,
At this point, NO _X reduction cannot be expected under this pilot injection condition. For example, if a method of further increasing the pilot injection interval or reducing the pilot injection amount is used, NO _X and noise reduction can be expected at this point as well.

Data was similarly sampled in other operating regions, and in consideration of these data, the pilot injection was set to be performed 3 msec or more before the main injection at the time interval Δt in all operating regions. The reason is that combustion of pilot injected fuel is completed before main injection is performed,
This is because an appropriate amount of burnt gas is dispersed inside the combustion chamber and a complete internal EGR effect is provided when the main injection is performed, so that NO _X and noise are sufficiently reduced. Further, FIG. 15 shows a characteristic diagram of the pilot injection amount q. Here, the maximum pilot injection amount qma at low load
x is 3 mm ³ / st, 3 m toward the high load area
It was set to m ³ / st or less to reduce black smoke. The pilot injection amount q in the injection map Mp of FIG. 14 is set along the pilot injection amount q of FIG. Note that FIG.
Although the nine operating ranges are set in the injection timing and injection pressure calculation map of, the operating ranges may be set to other numbers.

When such an engine 1 is driven,
The ECU 66 executes a predetermined main routine, and reaches the injection amount calculation routine shown in FIG. 16 in the middle thereof. Here, in steps s1 and s2, the operating information of each engine is fetched from each sensor and the current operating range is calculated. In this case, the ECU 66 determines the current engine speed Ne.
And the engine load L are taken in. Next, the engine speed thresholds Ne1 and Ne2 (see FIG. 14) between the adjacent operation ranges set for each operation range E and the current engine speed Ne are compared, and which engine is Ne is determined. It is determined whether the rotation speed is between the threshold values. Similarly, each operating range E
The engine load thresholds L1 and L2 (see FIG. 14) between the adjacent operation ranges set for each of them are compared with the current engine load L to determine which engine load L is between which thresholds. to decide. The current operating range En is determined from the position on the operating range determined by the engine speed and the load.

In step s3, based on the current operating range En calculated in this way, from the injection map Mp of FIG. 14, the injection timing T at that time, the interval Δθ (Δt) between the pilot injection timing tp1 and the main injection timing t1. , The pilot injection amount q, the main injection amount Q, and the injection pressure p are sequentially calculated, and the pilot injection start timing tp1, the pilot injection stop timing tp2, the main injection start timing t1, and the main injection end timing t2 are calculated according to these data. It is calculated and returns to the main routine (not shown). During this period, the ECU 66 continuously counts the crank angle dθ and detects the reference crank angle position θ0 of each cylinder.

When the reference crank angle position θ0 is detected during the control of the main routine, the ECU 66 proceeds to the solenoid valve drive routine of FIG. 17 as an interrupt process. Here, the latest count value is set in the injection timing control circuit of the corresponding cylinder that has reached the reference crank angle position θ0. That is, at step a1, the pilot on-counter in the injection timing control circuit is set to the pilot injection start timing tp1, and the pilot off counter is set to the pilot injection stop timing tp2. Further, in step a2, the main injection start timing t1 is set in the main injection start counter in the injection timing control circuit.
However, the main injection end timing t2 is set in the main injection end counter, each counter is started in step a3, and the process returns to the main routine (not shown).

As a result, when each counter completes counting and the pilot injection start timing tp1 is reached, the electromagnetic actuator 40 of the first three-way electromagnetic valve 34 is turned on,
The normally closed nozzle needle 18 is opened to perform the injection of the set injection amount during the pilot injection period until the pilot injection end timing tp2. Next, pilot injection timing tp1
When the main injection start timing t1 is reached after the time interval Δt (the time corresponding to the interval Δθ) between the main injection timing t1 and the main injection timing t1, the electromagnetic actuator 40 of the first three-way solenoid valve 34 is driven on.
The normally closed nozzle needle 18 is opened, and the set injection amount is injected during the main injection period until the main injection end timing t2.

Further, the ECU 66 drives the spill valve 64 via an electromagnetic actuator 62 (not shown) to control the pressure of the fuel pressure sensor 74 so as to be a pressure set by an injection pressure Pn map (not shown). As a result, at the injection pressure Pn set according to the current operating range En, the pilot injection and the main injection are performed from the fuel injection valve 10 at the set injection timing T with a time interval Δt (a time corresponding to the interval Δθ). It will be.

As a result, in all operating ranges E1 to E9,
As shown in FIGS. 2 (a) and 2 (b), the fuel injected by the fuel injection valve 10 has good directivity, collides with the collision wall surface 903, and is diffused and distributed in the combustion chamber C to complete the combustion. Then, as shown in FIGS. 3A and 3B, after the time interval Δt (the time corresponding to the interval Δθ) elapses, the injected main injected fuel collides with the collision wall surface 903, and the fuel particles squish. It receives the flow SK and diffuses into the combustion chamber C. FIG.
As shown in (a) and (b), the main injection fuel that collides with the collision wall surface 903 and is diffused and distributed in the combustion chamber C mixes with the air in the combustion chamber to perform main combustion. In this main combustion, the burnt gas produced by burning the pilot injected fuel brings out the internal EGR effect, and NO _X can be reduced.

Further, by shortening the ignition delay by the pilot injection, noise reduction can be achieved, which is advantageous. 13 (a) to 13 (c), the NO _x generation amount obtained according to the change of the crank angle interval Δθ under the respective operating conditions (operating ranges E1, E2, E3) of FIGS. 10 to 12. The characteristic diagram of g / kWh is shown. Here, in each of the cases of 20% and 40% load shown in FIGS. 13A and 13B, the effect of reducing NO _X is clear when the crank angle interval Δθ is 25 deg or more, and is shown in FIG. 13C. When the load is 80%, there is no increase or decrease in NO _X , but from this result, it is clear that the present invention can also achieve the effect of reducing NO _X in the medium to low load range.

As described above, the diesel engine combustion apparatus of FIG. 1 projects the fuel from the fuel injection valve 10 to the projection 902.
Is made to collide with and diffuse the fuel, and then the ECU 66 for controlling the injection timing T and the injection amount Q of the fuel performs pilot injection at Δθ before a predetermined time of the main injection timing. Therefore, the fuel spray pilot-injected into the combustion chamber C sufficiently mixes with the air in the combustion chamber and completes the combustion, and then the main injection is performed, so that the internal EGR is performed.
The effect of can be expected, ignition delay can be shortened, combustion can be mild, and low NO _x and low noise can be achieved.

In particular, the diesel engine combustion apparatus shown in FIG. 1 has a pressure accumulating chamber 36 in which the fuel supplied from the supply pump 38 is temporarily stored, and a first three-way type in which the fuel from the pressure accumulating chamber 36 is switched between injection and non-injection. A fuel supply unit A having a solenoid valve 34 is provided, and pilot injection and main injection are performed by switching control of the first three-way solenoid valve 34 during fuel injection by the ECU 66. Therefore, the main injection timing and the pilot injection can be surely executed, the effect of the internal EGR can be expected, the ignition delay can be shortened, the combustion becomes mild, and the low NO _x and the low noise can be achieved.

Further, the combustion device of the diesel engine of FIG. 1 is 3 m away from the start timing of the main injection by the ECU 66.
The first three-way solenoid valve 34 is switched and controlled so that the pilot injection is started before sec or more. Therefore, it is possible to surely complete the combustion of the fuel particles pilot-injected well before the main injection timing, to expect the effect of internal EGR sufficiently, to shorten the ignition delay, and to make the combustion mild and reduce the NO _x and low noise can be achieved. Further, in the diesel engine combustion device of FIG. 1, the injection hole 12 of the fuel injection valve 10 is directed vertically downward toward the projection 902, and the length 1 of the injection hole 12 is larger than three times the injection hole diameter d. Therefore, it is possible to prevent variations in the spray distribution at the time of injection, and
2 can stabilize the diffusion of combustion particles after collision with the fuel particles, can reliably burn the fuel particles, can expect the effect of internal EGR sufficiently, can shorten the ignition delay, and make the combustion mild and low. NO _x and low noise can be achieved.

[0038]

As described above, according to the first aspect of the present invention, the projection for fuel collision is raised at approximately the center of the bottom surface of the combustion chamber, and the fuel from the fuel injection valve is made to collide with the projection and diffused. In addition, after that, pilot injection is performed before the predetermined time of the main injection timing by the fuel supply control means that controls the injection timing, the injection pressure, and the injection amount of the fuel. For this reason, there is a time lag between the main injection timing and the pilot injection for a predetermined time or more, and the main injection is performed after the pilot-injected fuel spray has completed combustion and diffused, and the effect of internal EGR can be expected, and the ignition delay is delayed. Can be shortened, mild combustion is possible, and low NO _x and low noise can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine combustion apparatus as an embodiment of the present invention.

2A and 2B are injection operation explanatory views of the diesel engine combustion apparatus of FIG. 1 during pilot injection, in which FIG. 2A is a side sectional view thereof, and FIG.

3A and 3B are explanatory views of a diffusion operation of a main-injected spray after a pilot injection of the diesel engine combustion apparatus of FIG. 1 by a squish flow, in which FIG. 3A is a side sectional view thereof, and FIG. .

FIG. 4 is an explanatory view of injection operation during main injection of the combustion device for the diesel engine of FIG. 1, in which (a) is a side sectional view thereof,
(B) is a plan view.

5 is a characteristic diagram illustrating injection timings, injection intervals, and injection rates of pilot injection and main injection of the diesel engine combustion device of FIG.

FIG. 6 is a partial cross-sectional view of a needle valve portion of a fuel injection valve used in the diesel engine combustion device of FIG.

7 is a spray angle-L / D characteristic diagram used in setting the shape of the injection hole of the fuel injection valve used in the combustion device of the diesel engine of FIG. 1. FIG.

8 is a flow rate distribution-angle characteristic diagram used for setting the shape of the injection hole of the fuel injection valve used in the combustion device of the diesel engine of FIG.

9 is a characteristic diagram of deviation angle in the injection direction used in setting the shape of the injection hole of the fuel injection valve used in the combustion device of the diesel engine of FIG. 1-measurement number of times.

FIG. 10 is a graph showing characteristics of temperature, heat generation rate, and cylinder pressure according to changes in crank angle, which are used in setting an interval between pilot injection timing and main injection timing adopted by a control device for a normal diesel engine combustion device. It is a diagram and shows a characteristic diagram in a 20% load region.

FIG. 11 is a graph showing characteristics of temperature, heat release rate and in-cylinder pressure according to crank angle change, which are used in setting an interval between pilot injection timing and main injection timing adopted by a control device for a normal diesel engine combustion device. It is a diagram and shows the characteristic diagram in a 40% load range.

FIG. 12 shows characteristics of temperature, heat release rate, and cylinder pressure according to crank angle changes, which are used in setting the interval between the pilot injection timing and the main injection timing adopted by the control device for the combustion apparatus of a normal diesel engine. It is a diagram and shows a characteristic diagram in an 80% load region.

FIG. 13 is data of NO _X generation rate during operation of a normal diesel engine combustion device, (a) of 20
Data in% load range (corresponding to FIG. 10), 40% in (b)
Data in the load range (corresponding to FIG. 11) and (c) are data in the 80% load range (corresponding to FIG. 12).

FIG. 14 is an example of a schematic diagram of an injection map adopted in the control device for the combustion device of the diesel engine of FIG. 1.

FIG. 15 is an example of a schematic diagram of a pilot injection amount map adopted in the control device of the combustion device of the diesel engine of FIG. 1.

16 is a flowchart of an injection amount calculation program used by the control device for the diesel engine combustion device of FIG. 1. FIG.

FIG. 17 is a flowchart of an injection drive program used by the control device for the diesel engine combustion device in FIG. 1.

FIG. 18 is an injection operation explanatory view at the time of pilot injection of the direct injection type diesel engine, (a) is a side sectional view thereof,
(B) is a plan view.

FIG. 19 is an injection operation explanatory view at the time of main injection of a direct injection diesel engine, (a) is a side sectional view thereof, and (b) is a plan view.

FIG. 20 is an injection operation explanatory diagram of a conventional collision diffusion type diesel engine at the time of pilot injection, in which (a) is a side sectional view and (b) is a plan view.

FIG. 21 is an injection operation explanatory view of the conventional collision diffusion type diesel engine at the time of main injection, in which (a) is a side sectional view thereof,
(B) is a plan view.

[Explanation of symbols]

 8 Engine 801 Cylinder Head 9 Piston 901 Cavity 902 Collision Member 10 Fuel Injection Valve 12 Injection Port 16 Nozzle 34 First Three-way Solenoid Valve 36 Energy Storage 40 Electromagnetic Actuator 46 Energy Storage Fuel Supply Pump 62 Electromagnetic Actuator 64 Spill Valve 66 ECU 68 Cylinder Discrimination Device 70 Engine speed and crank angle detection device 72 Engine load detection device h Interval A Fuel supply means C Combustion chamber

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02M 61/14 310 F02M 61/14 310D 61/18 320 61/18 320Z

Claims (4)

[Claims] 1. A combustion chamber recessed in the top surface of a piston of a diesel engine, a fuel collision projection that is raised at approximately the center of the bottom surface of the combustion chamber, and a fuel collision projection that is arranged so as to oppose the fuel. And a fuel supply control means for controlling the injection timing and the injection pressure and the injection amount of the fuel injected from the fuel injection valve. The fuel supply control means controls the main injection timing of the main injection timing. A combustion device for a diesel engine, which performs pilot injection before a predetermined time. 2. A supply pump capable of varying a supply amount and an injection pressure by controlling a solenoid energization time, a pressure accumulating chamber for temporarily accumulating fuel supplied from the supply pump, and an injection of fuel from the pressure accumulating chamber. A fuel supply unit having a three-way electromagnetic valve for switching to non-injection, wherein the fuel supply control unit controls pilot switching and main injection by switching the three-way electromagnetic valve during fuel injection. The combustion device for a diesel engine according to claim 1, wherein the combustion device is a diesel engine. 3. The three-way solenoid valve is switched and controlled by the fuel supply control means so as to start the pilot injection 3 msec or more before the start timing of the main injection. Diesel engine combustion device. 4. The injection hole of the fuel injection valve is directed vertically downward toward the protrusion, and the length of the injection hole is larger than three times the diameter of the injection hole. Diesel engine combustion device.