JP2755419B2 - Hot surface collision ignition type internal combustion engine - Google Patents

Description

The present invention relates to a hot surface collision ignition type internal combustion engine.

[Conventional technology]

In a direct injection type diesel engine or a diesel engine with a sub-chamber, it is necessary to atomize the fuel injected from the fuel injection valve into the combustion chamber or the sub-chamber as much as possible and sufficiently mix it with air. When the fuel is injected from the nozzle port, the fuel is atomized as much as possible. Also, when the temperature of the combustion chamber or the sub-chamber is low, such as when starting the engine, atomization of the fuel is insufficient. Therefore, a glow plug is mounted in the combustion chamber or the sub-chamber to heat the air in the combustion chamber or the sub-chamber. In this way, fuel ignition is promoted.

[Problems to be solved by the invention]

However, the atomization of the fuel injected from the nozzle opening of the fuel injection valve is promoted in this way, and even if the glow plug is arranged in the combustion chamber or the sub-chamber, the fuel is sufficiently mixed with the air and the fuel is ignited. It takes a certain amount of time until this occurs, thus causing an ignition delay. When such an ignition delay occurs, when the ignition is performed, the surrounding fuel is rapidly burned because a large amount of fuel particles are already present in the surroundings, so that the combustion pressure in the combustion chamber or the sub-chamber sharply increases. To rise. When the combustion pressure rises sharply, not only does the problem that loud noise occurs, but also the problem that a large amount of NOx is generated because the maximum combustion temperature increases. Further, in such a diesel engine, it is difficult to uniformly disperse the fuel in the combustion chamber or the sub-chamber, so that an area around the fuel particles where oxygen is insufficient is always generated. As a result, a large amount of particulates are generated in such a region. As long as fuel is atomized and injected from the nozzle port of the fuel injection valve, it is difficult to shorten the ignition delay, and it is difficult to uniformly disperse the fuel in the combustion chamber or the sub-chamber. Therefore, as long as the fuel is injected while being atomized from the nozzle port of the fuel injection valve, a large noise is generated, a large amount of NOx is generated, and a large amount of particulates is generated.

Also, compression ignition engines have the advantage of high thermal efficiency. Therefore, it would be extremely economically advantageous if compression ignition of low cetane number and high octane number fuels such as gasoline and methanol could be performed. However, such low cetane number and high octane number fuels have an extremely long ignition delay period, and it has been conventionally difficult to ignite such fuels by compression ignition.

[Means for solving the problem]

In order to solve the above problems, according to the present invention, a cavity is formed on the top surface of the piston, and when the piston reaches the top dead center, the heating member of the electric heating type is located at the center of the cavity. The fuel injection valve is arranged so that the liquid columnar fuel is injected from the nozzle opening of the fuel injection valve toward the center of the substantially flat heating surface of the heating member, and the liquid columnar fuel collides with the heating surface.

[Action]

By colliding the fuel with the heating surface, the fuel particles received from the heating surface are promoted to be activated, are scattered around, and are immediately ignited. Therefore, the ignition delay is extremely shortened by using any fuel that can be used for an internal combustion engine such as gasoline, methanol, kerosene as well as light oil, and good combustion by self-ignition can be obtained.

〔Example〕

1 and 2 show a first embodiment according to the present invention.

1 and 2, reference numeral 1 denotes a cylinder block, 2 denotes a piston that reciprocates in the cylinder block 1, 3 denotes a cylinder head fixed on the cylinder block 1, and 4 denotes a piston 2 and a cylinder head 3. A combustion chamber 5 formed therebetween is designated by an intake valve, and 6 is designated by an exhaust valve. A cavity 7 is formed at the center of the flat top surface 2a of the piston 2, and a fuel injection valve 8 is arranged at the center of the flat inner wall surface 3a of the cylinder head 3. In the embodiment shown in FIG. 1, the fuel injection valve 8 has a single nozzle port 9 and a needle 10 for controlling the opening and closing of the nozzle port 9. When the needle 10 opens the nozzle port 9, the nozzle port 9 is closed. The fuel is injected toward the center of the cavity 7 from the.

At the center of the cavity 7, a disk-shaped heating member 13 supported by the cylinder head 3 via a pair of supporting members 11, 12 is arranged. The heating member 13 is formed from a heat-resistant material such as a ceramic. A heating element 14 that is electrically heated is disposed in the heating member 13, and the heating element 14 heats a heating surface 15 of the heating member 13 facing the nozzle port 9. In addition, a temperature sensor 16 that detects the temperature of the heating surface 15 and that includes, for example, a thermocouple is disposed in the heating member 13. The temperature of the heating surface 15 is maintained at a temperature of 650 ° C. or higher, for example, about 800 ° C., which is higher than the compression temperature, based on an output signal of the temperature sensor 16. The heating element 1
Instead of using 4, a ceramic heater such as a positive temperature coefficient thermistor element can be used for the entire heating member 13.
In the embodiment shown in FIG. 1, the heating surface 15 has a flat surface substantially parallel to the cylinder head inner wall surface 3a. However, the heating surface 15 can also be formed from a convex or concave surface having a relatively large radius of curvature.

Fuel is injected from the nozzle port 9 of the fuel injection valve 8 toward the center of the heating surface 15 in the form of a continuous liquid flow as indicated by F. In the embodiment shown in FIG. 1, this fuel injection is started from about 5 degrees before compression top dead center to about 15 degrees. The fuel injected from the nozzle port 9 collides with the central portion of the heating surface 15, and at this time, some fuel is immediately atomized by the collision energy, and the remaining fuel is in the form of a liquid film on the peripheral portion of the heating surface 15. It flows in all directions. This liquid film flow then splits at the periphery of the heating surface 15 into fuel particulates which scatter around as indicated by the arrows in FIG.
As described above, a part of the injected fuel is atomized immediately after the collision, but the atomized fuel takes heat from the heating surface 15 at the time of the collision and becomes high in temperature, so that the fuel is immediately self-ignited. Further, the fuel flowing in the form of a liquid film on the heating surface 15 takes heat from the heating surface 15 while flowing on the heating surface 15 and has a high temperature. Accordingly, the fuel particles scattered from the peripheral portion of the heating surface 15 to the periphery are also at a high temperature, so that the fuel particles are immediately self-ignited. Therefore, the ignition delay period becomes extremely short, and the fuel injected from the fuel injection valve 8 is burned sequentially. As a result, the generation of noise is suppressed because the combustion pressure rises slowly,
Further, since the maximum combustion temperature is lowered, generation of NOx is suppressed. Further, since the fuel is uniformly scattered in all directions from the heating surface 15, the fuel particles are uniformly dispersed in the cavity 7,
Thus, there is almost no region around the fuel fine particles where oxygen is deficient, so that the generation of particulates is suppressed.

What is important in the present invention is that fuel is injected from the nozzle port 9 of the fuel injection valve 8 in the form of a continuous liquid stream, and the injected fuel impinges on the heating surface 15 in a non-atomized liquid form; Injecting the liquid columnar fuel from the nozzle port 9 of the injection valve 8 to cause the liquid columnar fuel to collide with the heating surface 15 and to provide the heating surface 15 with sufficient heat to the fuel impinging on the heating surface 15 It has a sufficient area of a certain degree or more.

That is, unlike the conventional diesel engine in which the atomized fuel is ejected from the nozzle port of the fuel injection valve 8, the present invention basically provides the fuel injection when the fuel is injected from the nozzle port 9 of the fuel injection valve 8. Is not atomized, but the injected fuel is made to be atomized by colliding the injected fuel with the heating surface 15. Of course, it is impossible to prevent atomization of all the fuel injected from the nozzle port 9 and, therefore, in practice, a part of the fuel injected from the nozzle port 9 is heated in a non-atomized liquid form. It will hit the surface 15. The fuel is then heated on a heated surface in the form of a continuous liquid stream.
In some cases, it may impinge on the heating surface 15 in the form of a mass of liquid that splits after being ejected. In any case, in the present invention, the injected fuel is made to be atomized by colliding with the heating surface 15, so that it is necessary to cause the injected fuel to collide with the heating surface 15 at as high a speed as possible. The fuel is injected in the form of a continuous liquid stream, that is, in the form of a liquid column.
That is, since the fuel injected in the form of the continuous liquid flow has a large penetration force, it is hardly decelerated until it collides with the heating surface 15, and thus the fuel injection pressure of the fuel injected from the fuel injection valve 8 is reduced to 100 kg. / from cm ² as 150 kg / cm ² about low pressure can be allowed to impinge on the heated surface 15 of the injected fuel at a high speed.

In the case where the atomized fuel is injected from the nozzle port of the fuel injection valve as in the related art, the penetrating force of the fuel spray is small, and the fuel particles are rapidly decelerated as soon as they are injected from the nozzle port. Therefore, even if a glow plug is placed in such a fuel spray, a small amount of fuel particles that have collided with the glow plug are only floating near the glow plug, and high-temperature fuel particles are spread over a wide area in the combustion chamber 4. Since it is not dispersed, the effect of reducing the ignition delay is small.

Even if a part of the injected fuel is atomized immediately after the collision, the fuel colliding on the heating surface 15 in a liquid form spreads in a ring on the heating surface 15, and the fuel spread in a ring is atomized. Accordingly, in order to provide sufficient heat to the annular fuel, the heating surface 15 preferably has an area capable of heating at least the annular fuel. Also,
In order to sufficiently heat the fuel flowing in the form of a liquid film on the heating surface 15 toward the periphery thereof, the heating surface 15 preferably has a larger area.

Further, since the heating surface 15 is maintained at a high temperature, no carbon or the like is deposited on the heating surface 15, and since the size of the heating member 13 is small, when the heating element 14 is energized, the heating surface 15 Immediately rises, and good combustion with an extremely short ignition delay period from the start of the engine can be ensured.

3 to 12 show various embodiments. These third
1 and 2 in each embodiment shown in FIGS.
Components similar to those in the embodiment shown in the figures are denoted by the same reference numerals.

FIG. 3 shows a second embodiment. In this embodiment, the heating member 13 is integrally formed with a heat receiving portion 13a having a large number of annular fins formed below. The heat receiving part 13a is provided to absorb as much heat of the combustion gas as possible and to transfer this heat to the heating surface 15, thereby reducing the power consumption of the heating element 14.

FIG. 4 shows a third embodiment. In this embodiment, the support member
A heating element 14 is disposed in the inside of the support member 14, and a heating plate 17 made of, for example, a metal material having good heat conductivity is fixed to the tip of the support member 14. The heat generated from the heating element 14 is transferred to the heating plate 17 by heat conduction, thereby heating the heating surface 15 of the heating plate 17.

FIG. 5 shows a fourth embodiment. In this embodiment, the heating member
13 is supported by the fuel injection valve 8 via three support members 18. That is, in this embodiment, the heating member 13 is formed integrally with the fuel injection valve 8.

FIG. 6 shows a fifth embodiment. In this embodiment, the heating member
13 is supported by the center of the bottom wall surface of the cavity 7 formed in the piston 2.

FIG. 7 shows a sixth embodiment. In this embodiment, the cavity 7 formed in the piston 2 has a substantially spherical shape, and the heating member 13 is disposed on the peripheral wall surface of the spherical cavity 7. Fuel is injected from the nozzle port 9 of the fuel injection valve 8 toward the heating surface 15 of the heating member 13 as indicated by F.

FIG. 8 shows a seventh embodiment. In this embodiment, a pair of heating members 13 are arranged around the cavity 7, and each of these heating members 13 is supported by the cylinder head 3 via a corresponding supporting member 19. The fuel injection valve 8 has a pair of nozzle ports 9, and fuel is injected from each nozzle port 9 toward the corresponding heating surface 15 of the heating member 13.

FIG. 9 shows an eighth embodiment. In this embodiment, the entire top surface 2a of the piston 2 is formed flat, and a cavity 20 is formed at the center of the cylinder head inner wall surface 3a. A pair of heating members 13 are arranged on the peripheral wall surface of the cavity 20. The fuel injection valve 8 has a pair of nozzle ports 9, and fuel is injected from each nozzle port 9 toward the corresponding heating surface 15 of the heating member 13.

FIG. 10 shows a ninth embodiment. Also in this embodiment, the entire top surface 2a of the piston 2 is formed flat, and a cavity 20 is formed at the center of the cylinder head inner wall surface 3a. In this embodiment, the heating member 13 has an annular shape, and the annular heating member 13 is attached to the tip of the fuel injection valve 8. The fuel injection valve 8 has a plurality of nozzle ports 9, and fuel is injected from each nozzle port 9 toward a conical heating surface 15.

FIG. 11 shows a tenth embodiment. In this embodiment, the combustion chamber 4
Are the main chamber 4a and the sub-chamber 4b connected to the main chamber 4a through the nozzle 21.
The nozzle port 9 of the fuel injection valve 8 is disposed in the sub chamber 4b. A heating member 13 is disposed on the inner peripheral surface of the sub-chamber 4b, and fuel is injected from a nozzle port 9 of the fuel injection valve 8 toward a heating surface 15 of the heating member 13.

FIG. 12 shows an eleventh embodiment. Also in this embodiment, the combustion chamber 4
Are the main chamber 4a and the sub-chamber 4b connected to the main chamber 4a through the nozzle 21.
The nozzle port 9 of the fuel injection valve 8 is disposed in the sub chamber 4b. A heating member 13 supported by the inner wall surface of the sub-chamber 4b via a support member 22 is disposed at the center of the sub-chamber 4b, and is directed from the nozzle port 9 of the fuel injection valve 8 to the heating surface 15 of the heating member 13. Fuel is injected.

In any of the internal combustion engines shown in FIGS. 1 to 12, not only light oil but also gasoline, methanol, kerosene, and all other types of fuels usable in internal combustion engines can be used as fuel. Also, in any of the internal combustion engines shown in FIGS. 1 to 12, no throttle valve is provided in the intake passage, and since there is no need to generate swirl in the combustion chamber 4 or the main chamber 4a, the intake The resistance is reduced, and the thermal efficiency can be improved in this sense as well.

In any of the embodiments, it is necessary to maintain the temperature of the heating surface 15 at the target temperature in order to reduce the ignition delay.
This target temperature has an optimum value. This optimal value is almost
It is 650 ° C. or higher, preferably about 800 ° C., but slightly fluctuates depending on the operating state of the engine. Next, the optimum target temperature will be described with reference to FIG.

When the engine load L decreases, the amount of injected fuel decreases, and the temperature in the combustion chamber 4 or the sub-chamber 4b decreases. Therefore, as shown in FIG. 13 (A), as the engine load L decreases, the target temperature of the heating surface 15 increases.
It is preferable to increase T ₀ .

In addition, the lower the engine speed N, the longer the interval between the explosion strokes, and the lower the temperature in the combustion chamber 4 or the sub chamber 4b, making it difficult for self-ignition to occur. Therefore it is preferable to Figure 13 the engine rotational speed N as shown in (B) is to increase the target temperature T ₀ of the heating surface 15 in accordance lowered.

Further, the lower the engine cooling water temperature, the lower the intake air temperature, and the lower the temperature in the combustion chamber 4 or the sub-chamber 4b, so that it is difficult to self-ignite. Therefore, as shown in FIG. 13 (C), as the engine cooling water temperature TW decreases, the heating surface 15
It is preferable to increase the target temperature T ₀ of the.

Accordingly, as shown in FIG. 13 (D), the target temperature T ₀ of the heating surface 15 is the engine load L, the engine speed N, and the engine cooling water temperature TW.
Is a function of

Referring now to Figure 17 from Figure 14 illustrating a method for controlling the target temperature T _0.

In Figure 14 shows an electronic control unit used for controlling the target temperature T _0. This electronic control unit as shown in FIG.
30 is a digital computer and has a bidirectional bus 31.
(Read Only Memory) 3 interconnected by
2. It includes a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. The load sensor 37 generates an output voltage proportional to the amount of depression of an accelerator pedal (not shown), that is, an output voltage proportional to the engine load L. This output voltage is input to the input port 35 via the AD converter 38. You. The rotation speed sensor 39 generates an output pulse every time the engine crankshaft rotates 30 degrees, for example, and this output pulse is input to the input port 35.
The CPU 34 calculates the engine speed N from the output pulse. The temperature sensor 16 generates an output voltage proportional to the temperature T of the heating surface 15, and this output voltage is input to the input port 35 via the AD converter 40. The water temperature sensor 41 generates an output voltage proportional to the engine cooling water temperature TW, and this output voltage is input to the input port 35 via the AD converter 42. On the other hand, the output port 36 is connected to the heating element 14 of the heating member 13 via the drive circuit 43.
Connected to.

The relationship between the target temperature T ₀ , the engine load L, the engine speed N, and the engine cooling water temperature TW shown in FIG. 13 (D) is stored in advance in the ROM 32 in the form of a three-dimensional map. number sensor 39, the target temperature T ₀ determined based on the output signal of the water temperature sensor 41. The temperature T of the heating surface 15 of the heating member 13 is detected by the temperature sensor 16, heating element 14 is controlled such that the temperature T of the heating surface 15 becomes the target temperature T _0.

FIG. 15 shows a first embodiment of a heating control routine of the heating element 14, which is executed by interruption every predetermined time.

The temperature T of the heating surface 15, first, at step 50 and reference to FIG. 15 is higher or not than the target temperature T ₀ is determined. Proceed to step 51 if T> T ₀ the heating element 14
Is stopped. On the other hand, are energized heating element 14 proceeds to step 52 to be in TT _0, resulting heating element 14 is made to heat. In this way the heating surface 15
The temperature T of is controlled to the target temperature T _0. Note that the engine high-load operation is performed to increase the temperature of the combustion gas, and the temperature T of the heating surface 15 continues to be higher than the target temperature T ₀ even when the heating element 14 is not energized by the heat receiving action from the combustion gas. There are cases. In this case, the process proceeds from step 50 to step 51, in which the power supply to the heating element 14 is stopped.

FIG. 16 shows a second embodiment of the heating control routine of the heating element 14, which is executed by interruption every predetermined time.

The temperature T of the heating surface 15, first, at step 60 and reference to FIG. 16 whether higher than the target temperature T ₀ is determined. When T> T _0, the process proceeds to step 61 and the heating element
The current I supplied to 14 is reduced by a constant value α. Note that the heating element 14 has a current I supplied to the heating element 14.
Decreases, the amount of heat generation decreases, and as the current I increases, the amount of heat generation increases. Next, at step 62, it is determined whether or not the current I is negative. If I <0, the routine proceeds to step 63, where I = 0, and the routine proceeds to step 64.

On the other hand, the current I supplied to the heating element 14 proceeds to step 65 is made to increase by a predetermined value α when it is determined that the TT ₀ in step 60. Then step 66
In whether the current I is greater than the allowable maximum current I _max is determined, the routine proceeds to step 67, if I> I _max I = I _max
And proceed to Step 64.

In step 64, data representing the current I is output from the output port 36.
And the current value supplied to the heating element 14 is controlled based on this data. In this embodiment the current I supplied to the heating element 14 so that the temperature T of the heating surface 15 becomes the target temperature T ₀ is controlled. The energization of the heating element 14 is caused to stop even when the temperature of the even heating surface 15 without energizing the heating element 14 by heat effects from the combustion gases continue to be higher than the target temperature T ₀ in this embodiment.

FIG. 17 shows a third embodiment of the heating control routine of the heating element 14, which is executed by interruption every predetermined time.

Referring to FIG. 17, first, in step 70, it is determined whether or not the temperature T of the heating surface 15 is lower than a temperature (T ₀ −ΔT) obtained by subtracting a constant value ΔT from the target temperature T ₀ .
When T <(T ₀ −ΔT), the routine proceeds to step 71, where the current I supplied to the heating element 14 is set to the allowable maximum current I _max, and the routine proceeds to step 72. On the other hand, if T (T ₀ −ΔT), the routine proceeds to step 73, where it is determined whether or not the temperature T of the heating surface 15 is higher than the temperature (T ₀ + ΔT) obtained by adding the constant value ΔT to the target temperature T _0. . If T> (T ₀ + ΔT), step 74
The current value I supplied to the heating element 14 is made zero,
Next, the routine proceeds to step 72.

On the other hand, if it is determined in step 73 that T (T ₀ + ΔT), the process proceeds to step 75 where it is determined whether the temperature T of the heating surface 15 is higher than the target temperature T ₀ . When the T> T ₀ the current I supplied to the heating element 14 proceeds to step 76 is made to decrease by a predetermined value alpha. As described above, the heating element 14 generates less heat when the current I supplied to the heating element 14 decreases, and increases when the current I increases. Next, at step 77, it is determined whether or not the current I is negative. If I <0, the routine proceeds to step 78, where I = 0.
And proceeds to step 72.

On the other hand, the current I supplied to the heating element 14 proceeds to step 79 is made to increase by a predetermined value α when it is determined that the TT ₀ in step 75. Then step 80
In whether the current I is greater than the allowable maximum current I _max is determined, the routine proceeds to step 81, if I> I _max I = I _max
And proceeds to step 72.

In step 72, data representing the current I is output to the output port 36.
The current value supplied to the heating element 14 is controlled based on this data. In this embodiment, when the temperature T of the heating surface 15 is lower than the target temperature T ₀ by ΔT or more, the current I
There heating member 13 because it is the allowable maximum current I _max is caused to rapidly heated. Therefore, good combustion can be ensured immediately after the start of the engine. The current I is zero when the temperature T of the heating surface 15 is higher ΔT higher than the target temperature T _0, hence the energization of the heating element 14 is stopped. Therefore, if the temperature of the heating surface 15 continues to be higher than (T ₀ + ΔT) even if the heating element 14 is not energized by the heat receiving action from the combustion gas, the energization to the heating element 14 is stopped.
On the other hand, in the case of (T ₀ + ΔT) T (T ₀ −ΔT), the current I supplied to the heating element 14 is controlled so that the temperature T of the heating surface 15 becomes the target temperature T ₀ .

〔The invention's effect〕

Since the ignition delay period becomes extremely short, the fuel injected from the fuel injection valve is sequentially burned. As a result, the occurrence of noise due to a gradual rise in combustion pressure is suppressed,
Further, since the maximum combustion temperature is lowered, generation of NOx is suppressed. Furthermore, since the heating member is arranged so that it is located in the center of the cavity when the piston reaches the top dead center, the fuel scatters uniformly from the heating surface in all directions, and the fuel particles are evenly distributed in the cavity. Are distributed. As a result, there is almost no oxygen-deficient region around the fuel particles, so that the generation of particulates is suppressed.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a first embodiment of a hot surface collision ignition type internal combustion engine, FIG. 2 is a diagram showing an inner wall surface of a cylinder head of FIG. 1, and FIG. FIG. 4 is a side sectional view of a third embodiment of the hot surface collision ignition type internal combustion engine, FIG. 5 is a side cross sectional view of the fourth embodiment of the hot surface collision ignition type internal combustion engine, FIG. 6 is a side sectional view of a fifth embodiment of the hot surface collision ignition type internal combustion engine, FIG. 7 is a side sectional view of the sixth embodiment of the hot surface collision ignition type internal combustion engine, and FIG. FIG. 9 is a side sectional view of a seventh embodiment of the internal combustion engine of the hot surface collision ignition type, and FIG.
FIG. 11 is a side cross-sectional view of a ninth embodiment of the hot surface collision ignition type internal combustion engine, FIG. 11 is a side cross sectional view of the tenth embodiment of the hot surface collision ignition type internal combustion engine, and FIG. FIG. 13 is a diagram showing a target temperature, FIG. 14 is a circuit diagram of an electronic control unit, FIG. 15 is a flowchart of a first embodiment for performing heating control, FIG. FIG. 16 is a flowchart of the second embodiment for performing the heating control, and FIG. 17 is a flowchart of the third embodiment for performing the heating control. 8: fuel injection valve, 13: heating member, 14: heating element, 15: heating surface.

Claims (1)

(57) [Claims] 1. A fuel injection valve having a cavity formed on a top surface of a piston, wherein an electric heating type heating member is arranged so as to be located at a central portion in the cavity when the piston reaches a top dead center. A hot surface collision ignition type internal combustion engine in which a liquid columnar fuel is injected from a nozzle port toward a central portion of a substantially flat heating surface of the heating member, and the liquid columnar fuel collides with the heating surface.