JPS63272970A - Direct injection engine - Google Patents

Abstract

PURPOSE:To improve the fuel consumption and output of a direct injection engine in an overall load range by providing a glow plug and a spark plug as means for ignition of fuel injected into a cavity, and operating the plugs selectively in low and high load ranges of the engine. CONSTITUTION:A fuel injection valve 5, a glow plug 6 and a spark plug 7 are provided on the cylinder head 2 of an engine 1 such that they face a cavity 4 formed on the top face 3a of a piston 3 at the top dead point of the piston 3, respectively. In this case, the glow plug 6 is provided, for example, on the first fuel spray line 31A of the fuel injection valve 5 and between the fuel injection valve 5 and a cavity peripheral wall 4a. On the other hand, the spark plug 7 is, for example, provided on lower stream side from swirl than the second fuel spray line 31B of the fuel injection valve 5 and between the fuel injection valve 5 and the cavity peripheral wall 4a. The plugs 6, 7 are, therefore, selectively operated in a low load range or high load range of the engine 1, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a direct injection engine, and more particularly to a direct injection engine that uses low cetane fuel and combusts it using auxiliary ignition means.

(Prior Art) In recent years, in the field of diesel engines, attempts have been made to use low cetane number fuels such as ethanol, which have inferior ignitability than light oil.

In this case, the biggest problem is the poor ignitability due to the low cetane number fuel, and combustion by compression ignition is difficult with compression comparable to that of a conventional diesel engine.

For this reason, for example, as disclosed in Japanese Unexamined Patent Publication No. 59-150923, a so-called spark assist diesel engine is provided with a spark plug as an auxiliary ignition means and uses this spark plug to forcibly ignite low cetane fuel. is proposed.

By the way, currently, as a forced ignition method, a spark plug is used as in the above-mentioned known example.

The spark direct ignition method, which directly ignites the fuel, and the hot surface ignition method, which uses a glow plug and vaporizes the fuel near the surface of the glow plug and ignites it, are known, but both of these methods are described below. Each has its own drawbacks.

(In the case of a spark ignition type diesel engine) (1) Fuel consumption deteriorates and output torque decreases in a high load range. That is, in a low load range, the atmospheric temperature inside the cavity is low and therefore it is difficult to vaporize the fuel. For this reason, in such low load ranges, forced ignition using sparks stabilizes combustion and maintains high levels of fuel efficiency and output performance, but this type of spark ignition is not used in medium and high load ranges. In this case, the high ambient temperature inside the cavity causes this spark plug part to become a heat point, making the ignition timing unstable.
Irregular combustion leads to deterioration in fuel efficiency and output performance.

(2) Due to the high compression ratio and high heat load, the electrodes of the spark plug are subject to severe wear, especially in the high load range where the heat load increases.

(For diesel engines with hot surface ignition system) (1)
In the low load range, fuel efficiency deteriorates and output torque decreases. In other words, in a high load range where the ambient temperature inside the cavity itself is high, the glow plug heats the fuel and promotes vaporization, which facilitates ignition combustion and maintains good fuel efficiency and output performance. In a low load range where the glow plug itself is low, it is difficult to sufficiently vaporize the fuel to avoid ignition and combustion by the thermal action of the glow plug, and this also causes deterioration of fuel efficiency and output performance due to irregular combustion.

(Object of the Invention) The present invention aims to solve the problems pointed out in the above-mentioned section of the prior art, and aims to improve fuel efficiency and output performance in the entire engine load range in a direct injection engine equipped with an auxiliary ignition means. The purpose is to maintain.

(Technical Background of the Invention) In the process of researching means for realizing the fuel efficiency and output performance of a direct injection engine equipped with auxiliary ignition means within a wider operating range of the engine, the inventors of the present invention The fuel efficiency characteristics of a spark ignition type diesel engine with only a spark plug as an auxiliary ignition means versus engine load, and the fuel efficiency characteristics of a hot surface ignition type diesel engine with only a glow plug as an auxiliary ignition means with respect to engine load, respectively. The results are shown in Figure 24.

As a result of considering this Figure 24, the inventors of the present invention found that when comparing the characteristics of a spark ignition type diesel engine and the characteristics of a hot surface ignition type diesel engine relatively, in a low load range, the spark ignition type diesel engine The fuel efficiency of the hot surface ignition diesel engine is better than that of the hot surface ignition diesel engine, and on the other hand, in the high load range, the fuel efficiency of the hot surface ignition diesel engine is better than that of the spark ignition diesel engine. I found out that.

Based on this, the inventors of the present application have provided one engine with two auxiliary ignition means, a spark plug and a glow plug, and in the low load range of the engine, the spark plug acts to improve the fuel efficiency of a spark ignition type diesel engine. In addition, in the high load range of the engine, the glow plug is activated to obtain the fuel efficiency characteristics of a hot surface ignition type diesel engine, thereby achieving high standards of fuel efficiency and output characteristics over the entire engine load range. This is what I came up with. “(Means for achieving the object) The present invention is based on this technical background, and as a means for achieving the above object, an auxiliary ignition means is provided facing the engine cavity. , a direct injection engine in which the fuel injected into the cavity is combusted by the auxiliary ignition means, which includes a glow plug and a spark plug as the auxiliary ignition means, and the spark plug is used in a low load range of the engine. In addition, the glow plugs are selectively activated in the high engine load range.

(Function) In the present invention, by the above means, the fuel is directly ignited and combusted by the spark of the spark plug in the low load range where the atmospheric temperature inside the engine cavity is relatively low and the vaporization effect of the fuel is poor. On the other hand, in high load ranges where the atmospheric temperature inside the cavity is relatively high and therefore fuel vaporization is relatively easy, the glow plug further promotes fuel vaporization and the fuel is easily ignited and combusted. .

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 to 23.

I-First Embodiment FIGS. 1 and 2 show the main parts of a direct injection engine according to the first embodiment of the present invention, and in each figure, 1 is a cylinder, and 2 is a cylinder. In the cylinder head, 3 is a piston. A circular concave cavity 4 is formed in the top surface 3a of the piston 3.

Further, a fuel injection valve 5, a glow plug 6, and a spark plug 7 are attached to the cylinder head 2 so as to face the cavity 4 near the top dead center of the piston.

This fuel injection valve 5, glow plug 6, and spark plug 7
The planar arrangement position of is set as shown in FIG. That is, the fuel injection valve 5 is arranged at a position slightly eccentric from the center of the cavity 4. Of the five fuel spray lines 31A to 31E extending radially around it,
A first fuel spray line 31A and a second fuel spray line 31 adjacent to the swirl downstream side with respect to the first fuel spray line 31A.
The mounting position in the rotational direction is set so that the two fuel spray lines B are directed toward the eccentric side of the fuel injection valve 5.

The glow plug 6 is arranged on the axis of the first fuel spray line 31A of the fuel injection valve 5 and at an intermediate position between the fuel injection valve 5 and the cavity peripheral wall 4a.

The spark plug 7 is arranged so as to be slightly offset toward the school downstream side from the axis of the second fuel spray line 31B of the fuel injection valve 5, and located between the fuel injection valve 5 and the cavity circumferential wall 4a. There is.

The arrangement of the glow plug 6 and the spark plug 7 is due to the following reasons. That is, the glow plug 6 is the fuel injection valve 5.
The purpose of this is to warm the fuel injected from the fuel itself, promote its vaporization, and lead to ignition.
This is because it is effective to be on the fuel spray line and directly exposed to the sprayed fuel. Further, the spark plug 7 sparks the combustible mixture when the fuel injected from the fuel injection valve 5 rides on the swirl and flows downstream and mixes with the air in the cavity 4 to become a combustible mixture. Since the spark plug 7 is directly ignited and burnt, it is preferable that the spark plug 7 be positioned slightly toward the downstream side of the swirl from the fuel spray line axis. It is arranged slightly downstream of the swirl of the fuel spray line 31B.

In FIG. 2, the reference numeral "it" is an intake boat, and 12 is an exhaust port.

By the way, this glow plug 6 and spark plug 7 are
When a low cetane number fuel (for example, ethanol) is used as a fuel, it functions as an auxiliary ignition means to help ignite it, and in this embodiment, the present invention is applied.
Both are selectively used depending on the engine load. In other words, as shown in Fig. 4, the engine operating range is divided into two areas: high load area and low load area, and these two areas -
Among these regions, a high load region is defined as a glow plug use region, that is, an operation region where only the glow plug is activated, and a low load region is defined as a spark plug usage region, that is, an operation region where only the spark plug 7 is activated.

Further, the selection of the glow plug 6 and the spark plug 7 is performed by selectively operating the spark plug ignition system 16 and the glow plug ignition system 17 by the controller 15, as shown in FIG. That is, signals corresponding to the engine speed, engine load, intake air temperature, and cavity wall temperature are input to the controller 15, respectively. Among these input signals, the controller 15 determines whether the engine load is the load Po shown in FIG. When the load is greater than the load applied to the glow plug ignition system 17, a glow plug activation signal S is sent to the glow plug ignition system 17.

When the load is smaller than the load Po, a spark plug activation signal Sl is output to the spark plug ignition system 16.

According to the direct injection engine having the ignition system configured as described above, the spark plug 7 operates in the low load range where the atmospheric temperature inside the cavity 4 is relatively low and therefore the vaporization of the fuel is low. The fuel (combustible mixture) in the cavity 4 is directly ignited by the spark generated from the cavity 4 and combusts. Therefore, even though low cetane number fuel, which originally has poor ignitability, is used, and the ambient temperature inside the cavity 4 (i.e., cavity wall temperature) is low, the vaporization effect of the fuel is at its worst in the low load range. The fuel is easily ignited and combusted stably, ensuring a high level of fuel efficiency and output performance (see FIG. 24).

On the other hand, in a high load range where the atmospheric temperature inside the cavity 4 is relatively high and fuel vaporization itself is relatively easy, the glow plug 6 acts instead of the spark plug 7, and the glow plug 6 prevents fuel vaporization. It is further promoted and easily leads to ignition.

When a flame nucleus is generated by ignition, combustion spreads from this flame nucleus to the surrounding area by flame propagation. Therefore, good ignitability and stable combustion can be obtained, and high levels of fuel efficiency and output performance can be achieved (see FIG. 24).

At the same time, since the spark plug 7 is not operated in a high load range, problems caused by this, that is, deterioration in fuel efficiency and output performance due to heat points, as pointed out in the section on the conventional example above, are avoided.

■-Second Embodiment The direct injection engine of the second embodiment has the configuration (hardware and software) explained in the first embodiment, and furthermore, the operating state of the engine changes from a low load range to a high load range. This is an additional configuration (software) to solve problems (described in detail later) when doing so.

When the operating state of the engine shifts from a low load range to a high load range, the auxiliary ignition means of the ignition system is switched from the spark plug to the glow plug (basic control similar to the first embodiment). However, if the configuration is such that when the engine load shifts from a low load range to a high load range, the spark plug 7 is stopped and the glow plug 6 is energized instead. After the transition, combustibility becomes unstable, resulting in a decrease in fuel efficiency and output performance. In other words, the engine has an ignition delay period as a potential cause, but in addition to this, the glow plug 6 does not instantly become red hot even when it is energized, but requires some time to heat up (internal). Furthermore, moving from a low load range to a high load range means that the amount of fuel injected increases, and the increase in the latent heat of vaporization of the fuel inhibits the temperature rise of the glow plug 6 (cooling Therefore, immediately after the transition from the low load range to the high load range, the glow plug 6 cannot sufficiently vaporize the fuel. As a result, combustion becomes unstable, leading to a decrease in fuel efficiency and output performance.

In order to prevent this, in this embodiment, when the operating state shifts from a low load range to a high load range, as shown in FIG. 5, the glow plug 6 and the spark plug 7 are switched at the same time as the load range changes. Instead, the spark ignition by the spark plug 7 is continued until the surface temperature of the glow plug 6 reaches an appropriate temperature even after the shift to the high load range. By doing so, combustion instability caused by insufficient surface temperature of the glow plug 6 immediately after the transition from the low load range to the high load range can be reliably prevented.

FIG. 6 shows an interesting control flowchart when performing the above control. That is, the engine load is read (step AI) and the engine load is the boundary load Po.
(Refer to Figure 4), the direction of the change is determined (Step A2), and when the transition is from a low load range to a high load range (i.e., the auxiliary ignition means is switched from the spark plug 7 to the glow plug 6). case), the glow plug 6 is first energized (step A3). Incidentally, at this time, the operation of the spark plug 7 continues as it is.

After the glow plug 6 is energized, the glow plug temperature is read (step A4), and it is determined whether the temperature has reached the appropriate temperature (step A5). When the glow plug temperature reaches the appropriate temperature, the operation of the spark plug 7 is stopped (step 86), and the operation is completely shifted to hot surface ignition operation using only the glow plug 6.

That is, after the transition from the low load area to the high load area, the predetermined time (T
During the period 0, the glow plug 6 and the spark plug 7 are used together.

Also, in the above explanation, the glow plug 6 and the spark plug 7
Although the period of combined use of the glow plug 6 is controlled by the temperature of the glow plug 6, it may also be controlled by, for example, the energization time (T, ) based on the time when the energization to the glow plug 6 is started.

(2)-Third Embodiment (1) Basic Structure FIGS. 7 and 8 show the main parts of a direct injection engine according to a third embodiment of the present invention. This direct injection engine basically has the same configuration as the direct injection engine of the first embodiment (see FIGS. 1 and 2),
In each figure, reference numeral 1 is a cylinder, 2 is a cylinder head, 3 is a piston, 4 is a cavity, 5 is a fuel injection valve, and 6 is a cylinder head.
1 is a glow plug, 7 is a spark plug, 11 is an intake boat, and 12 is an exhaust boat.

In addition, the control system of this direct injection engine basically uses the control system of the first embodiment (basic control, see FIGS. 3 and 4), but in this embodiment, New configurations (hardware and software) have been added, as described below, from the perspective of improving drivability, especially in extremely cold regions and in extremely low load areas such as starting, idling, and deceleration areas. These points will be explained in detail below.

(2) Problems specific to extremely cold regions In extremely cold regions, there are the following problems in terms of drivability in extremely low load regions compared to normal temperature regions.

(When starting) When using the spark ignition method, the extremely low temperature makes it extremely difficult to vaporize the fuel, making it difficult to form a flammable mixture, which causes spark plug fogging and makes starting difficult. .

When hot surface ignition using a glow plug is adopted, starting the engine becomes difficult because the ambient temperature inside the cavity is extremely low and the fuel cannot be ignited.

(During driving) During very low load operation such as idling or downhill driving, the intake air temperature is low and the amount of fuel injection is small, so the cavity wall temperature decreases and fuel vaporization becomes worse. Therefore, combustion becomes unstable regardless of whether spark ignition or hot surface ignition is employed.

Note that the medium load range falls within the glow plug use range according to the basic control explained in the first embodiment, but especially in extremely cold regions, the intake air temperature is lower than in normal temperature regions. The cavity wall temperature drops dramatically and the ignition delay increases.
Diesel knock will occur and fuel efficiency will deteriorate.

(3) Method for improving the above problem In order to avoid such problems peculiar to operation in extremely cold regions, the inventors of the present application first used a glow plug 6 and a spark plug 7 in combination in the extremely low load range. The idea was to sufficiently vaporize the fuel using the glow plug 6, and then ignite and burn it using the spark plug 7, thereby improving starting performance in extremely cold regions and running performance in extremely low load ranges. be.

Specifically, in terms of hardware, first, as shown in FIG. 8, the glow plug 6 is connected to the first fuel spray line 3 of the fuel injection valve 5.
The spark plug 7 is placed on the axis of the glow plug 1A, and the spark plug 7 is placed on the downstream side of the swirl with respect to the glow plug 6 and close to the glow plug 6 along the swirl direction. This makes it possible to ignite the fuel (combustible mixture) by the spark plug 7 and stably burn it, which is first sufficiently vaporized by the glow plug 6 and then flowed downstream by the swirl.

In terms of software, as shown in Figure 15, the control range of the ignition system can be divided into a glow plug usage range that belongs to a high load range, a spark plug usage range that belongs to a medium load range, and a glow plug usage range that belongs to an extremely low load range. It is divided into three stages, including the area where spark plugs are used.

In this way, the control range is divided into three stages depending on the load, and glow plugs 6 and spark plugs 7 are used together in the extremely low load range, so it is possible to operate in extremely cold regions as described below. More stable combustion ensures better startability and running performance.

(At the time of starting) At the time of starting, the glow plug 6 and the spark plug 7 are used together, the glow plug 6 promotes the vaporization of the fuel, and after a sufficient combustible mixture is formed, the spark plug 7 ignites it and burns it. Therefore, it is possible to start the engine easily even though the atmospheric temperature inside the cavity 4 is extremely low and it is difficult to vaporize the fuel. Therefore, the fogging phenomenon of the spark plug 7 does not occur, and fuel efficiency is also improved.

(During driving) When driving in an extremely low load range, that is, when driving downhill, decelerating, or idling, the above basic control (first
In the control of the embodiment described above, the spark is ignited by the spark plug 7, but in extremely cold regions, the vaporization state of the fuel is extremely poor, so if spark ignition is used, combustion becomes unstable. However, in this embodiment, the glow plug 6 and the spark plug 7 are used together, and after the fuel is vaporized by the glow plug 6, the spark ignites the combustible mixture, so a stable combustion state is not achieved. Ru.

On the other hand, in the medium load range, the spark plug 7 is used for the following reasons. In other words, the influence of ignition performance, ignition delay, etc. due to a decrease in the cavity atmosphere temperature is smaller in spark ignition by the spark plug 7 than in the case of hot surface ignition by the glow plug 6, and more stable combustion is ensured. . In addition, in this case, the boundary load (Pl) between the spark plug usage area and the glow plug usage area is set to a higher load side than the boundary load (Po, Figures 4 and 15) during the above basic control. There is.

This is done in consideration of the fact that in extremely cold regions, the cavity atmosphere temperature corresponding to the engine load is relatively lower than in normal temperature regions.

(4) Improvements in warm-up operation Regarding warm-up operation in extremely cold regions, it is advantageous to use glow plug 6 and spark plug 7 in combination to obtain more stable combustion. On the other hand, when both are used together, power consumption increases, which is not preferable. However, as described above, if the power supply to the glow plug 6 is immediately stopped after starting and spark ignition is performed only by the spark plug 7, the combustion will become unstable, as described above. Therefore, in this embodiment, when starting and warming up in an extremely cold region, the glow plug 6 and spark plug 7 are used together to start the engine, as shown in FIG. 16, and then the cavity atmospheric temperature is set. Until the temperature (warm-up temperature) is reached, the glow plug 6 and the spark plug 7 are used together, and when the set temperature is reached, the energization to the glow plug 6 is stopped and only the spark plug 7 is operated. This ensures power savings and combustion stability during warm-up.

A control flowchart during this warm-up operation is shown in FIG. That is, after the switch is turned on, the outside air temperature (intake air temperature) is read (step B1), and based on it, it is determined whether or not warm-up is necessary (step B2).

Here, if the outside temperature is high and there is no need for warm-up, there is no need to perform the above-mentioned control, that is, it is sufficient to perform warm-up operation according to the control pattern of the basic control shown in Figure 4. outputs an ignition command for the spark plug 7 (Step B9), operates the starter, starts the engine by spark ignition, and then shifts to basic control (Step B8). On the other hand, if the outside temperature is low and it is necessary to warm up the engine, first preheat the glow plug 6 in step B3), then turn on the starter and start the engine by using both the glow plug 6 and the spark plug 7. (Step B4). After starting the engine, the engine shifts to warm-up operation (step B5). After shifting to the warm-up operation, the cavity ambient temperature is monitored, and the warm-up operation is continued until the ambient temperature reaches a predetermined temperature (step BS). When the above ambient temperature reaches the set temperature, it is determined that warming up is complete.
The energization to the glow plug 6 is cut off (step B7), and then the process shifts to basic control (step B8).

(5) Other arrangement examples of glow plugs and spark plugs In this example, as mentioned above, glow plugs 6 and spark plugs 7 are used together during extremely low load operation in extremely cold regions, and glow plugs 6 provide sufficient fuel. Along with vaporizing the
By igniting the combustible air-fuel mixture formed downstream of the glow plug 6 by the swirl using the spark plug 7 and combusting it, the intention is to facilitate starting in an extremely low temperature atmosphere and to obtain stable combustion. As mentioned above, And such an action
One example of a suitable arrangement of the glow plug 6 and spark plug 7 to obtain the effect has been shown and explained in FIGS. 7 and 8, but this arrangement example of the glow plug 6 and spark plug 7 In addition, various methods such as those described below can be considered. Below, nine examples of these other arrangements will be discussed.

(Other arrangement example!) A direct injection engine according to a first other arrangement example is shown in FIGS. 9 and 1θ. In this arrangement example, the glow plug 6 and the spark plug 7 are connected to the same fuel spray line 31A.
The glow plugs 6 are arranged close to each other with the glow plugs 6 positioned on the fuel injection valve 5 side. In this case, the fuel injected from the fuel injection valve 5, warmed by the glow plug 6, and vaporized is directly ignited by the spark plug 7, resulting in particularly good startability.

(Second Alternative Arrangement Example) FIGS. 11 and 12 show a direct injection engine according to a second alternative arrangement example. In this arrangement example, the cavity 4 is not circular but has an irregular shape having a corner portion 4b that bulges radially outward on one side, and the spark plug 7 is disposed in the corner portion 4b. , the glow plug 6 is arranged upstream of the spark plug 7 in the swirl direction and on the axis of the first fuel spray line 31A. In this case, the fuel injected from the fuel injection valve 5 and sufficiently vaporized by the glow plug 6 rides on the swirl and moves downstream. Since this corner portion 4b is formed, this corner portion 4b becomes a stagnation portion of the combustible air-fuel mixture. Therefore, ignition of the combustible mixture by the spark plug 7 becomes easier and more reliable, and startability is further improved.

(Third Other Arrangement Example) FIGS. 13 and 14 show a direct injection engine according to a third other arrangement example. This arrangement example is a modification of the second other arrangement example, in which the cavity 4 has an irregular shape with a corner portion 4b, and one of the fuel spray lines from the fuel injection valve 5, for example, the first fuel spray line 31
A is directed toward the corner portion 4b, and a glow plug 6 and a spark plug 7 are arranged in a line on this fuel spray line 31A, with the glow plug 6 being positioned on the fuel injection valve 5 side. .

In this case, after the sprayed fuel is vaporized by the glow plug 6, it directly moves to the spark plug 7 side, and the combustible mixture tends to accumulate in the corner portion 4b. Due to the synergistic effect, the second The ignitability of the fuel is even better than that of other arrangement examples.

This has the advantage of improved performance and easier start-up.

■-Fourth Embodiment The direct injection engine of the fourth embodiment has a problem with the configuration of the direct injection engine of the first embodiment described above due to ignition delay during acceleration in the range where glow plugs are used (described later). The hardware configuration of the engine (see Figures 1 and 2) and the control area of the ignition system (see Figure 4) are all the same as those of the first embodiment. to be used.

(1) Problems during acceleration in the glow plug usage range When the operating state shifts from steady operation to accelerated operation, the fuel injection amount increases rapidly (see the injection amount characteristic diagram in FIG. 20). For this reason, the latent heat of vaporization of the fuel increases, and its cooling effect lowers the surface temperature of the glow plug 6 in the glow plug usage area (see glow plug temperature in Figure 18), and the ignition delay period remains constant as shown in Figure 20. Sometimes the ignition delay period (to) due to latent factors in the engine is added as a result of internal factors due to the increase in latent heat of vaporization,
The ignition delay period (t,) is extended. As a result, the combustion state becomes poor due to worsening of flame propagation during combustion or misfire, and diesel knock becomes more likely to occur.

(2) Means for solving the above problem In order to solve the above problem, in this embodiment, as shown in FIG. The plug 6 and the spark plug 7 are used together. By doing this, even in a state where the surface temperature of the glow plug 6 decreases due to the latent heat of vaporization of the fuel and the vaporization effect of the fuel decreases somewhat, ignition combustion is performed by the spark plug 7, and an increase in ignition delay is prevented. This will suppress the occurrence of diesel knock.

FIG. 19 shows a flowchart of such ignition system control. To explain this, after starting the engine, first read the engine load (step CI), and then determine the control range of the ignition system based on this (step C2).
. If the result of the determination is that the glow plug is in use, then the accelerator opening degree is read and the rate of change in the opening degree is calculated (step C3), and it is determined whether acceleration is occurring (step C4).

As a result of the determination, if the vehicle is accelerating, the spark plug 7 is operated while the glow plug 6 is kept energized, and the glow plug 6 and the spark plug 7 are used together (step 05).

Next, read the temperature of the glow plug 6 (step C6
), when the surface temperature of the glow plug 6 rises to a temperature that is sufficient to ignite the glow plug 6 alone, the spark plug 7 is turned off (step C8), and the glow plug 6 is operated in the normal glow plug use range. Transition.

■-Fifth Embodiment The direct injection engine of the fifth embodiment has the structure of the direct injection engine of the first embodiment described above. A configuration is added to improve startability under conditions such as temperatures up to -20°C, for example. In other words, according to the basic control described above (see Figure 4), during starting, the spark plug is used and ignition is performed by the spark plug, but if this control is applied as is to starting in cold weather, the following will occur. A problem like this occurs.

(At the time of starting) When starting is performed by spark ignition, the cavity atmosphere temperature is low and the fuel vaporization state is poor, so a spark plug fogging phenomenon occurs, making starting difficult.

(After startup) If hot surface ignition operation using a glow plug is continued in a high load range after startup, the ignition delay will increase due to the low cavity ambient temperature, making diesel knock more likely to occur.

For this reason, in this embodiment, as shown in Fig. 21, ignition is performed using a preheated glow plug 6 to facilitate starting, and after starting, ignition is performed using a glow plug 6 that has been preheated to make the starting easier. The engine operates with only spark ignition in the operating range to suppress the occurrence of diesel knock.

Further, when the set temperature is reached, basic control is performed according to the control map shown in FIG.

Furthermore, in this embodiment, after spark ignition is performed until the cavity atmosphere temperature reaches the set temperature (the period shown as the correction period in FIG. 21),
Combustion is further stabilized by correcting and controlling the ignition period (discharge period) of the spark plug 7 according to the progress of warm-up (engine temperature). Specifically, as shown in Figure 22, when the engine is cold, the ignition period of the spark plug 7 is lengthened, and as the engine warms up, the ignition period is gradually shortened, and when the set temperature is reached, the basic control is started. I am trying to move it to .

A control flowchart of this ignition system is shown in FIG. To explain this, first read the current outside temperature (
Step DI), it is determined whether or not warm-up is necessary (Step D2).

As a result of the determination, if warm-up is not necessary, a spark plug ignition command is output (step DI2), and the engine is started (step D13).

After starting the engine, the process shifts to basic control (step D10).

On the other hand, if it is necessary to warm up the engine, first energize the glow plug to preheat it (step D3), and then start the engine (step D4).

When the engine completely explodes (step D5), a spark plug ignition command is output (step D6), and furthermore, the energization to the glow plug is stopped to shift to operation using only the spark plug (step D7).

After shifting to operation using only the spark plug, the warm-up operation is continued until the cavity wall temperature reaches a predetermined temperature (step D8), and when the temperature reaches the predetermined temperature, the routine shifts to basic control (step DIO).

Further, during the warm-up operation until the predetermined temperature is reached, the spark ignition period is controlled according to the control map shown in FIG. 22 (step Dll).

(Effects of the Invention) The present invention provides a direct injection engine in which an auxiliary ignition means is provided facing a cavity of the engine, and the fuel injected into the cavity is prevented from being combusted by the auxiliary ignition means. The engine is characterized in that it is equipped with a glow plug and a spark plug, and the spark plug is selectively activated in a low engine load range, and the glow plug is selectively activated in a high engine load range. .

Therefore, according to the direct injection engine of the present invention, in the low load range of the engine where the atmospheric temperature inside the cavity is relatively low and fuel vaporization is relatively poor, spark ignition is performed by the spark plug, while the atmospheric temperature inside the cavity is In the high-load range of the engine, where the fuel vaporization is relatively high and the fuel vaporization is relatively good, the glow plug performs hot surface ignition, so a high level of fuel efficiency and output performance can be achieved in the low-load and high-load ranges of the engine. It has the effect of being

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the main parts of a direct injection engine according to the first embodiment of the present invention, FIG. FIG. 4 is a control area diagram of the direct injection engine shown in FIG. 1, and FIG. 4 shows the ignition system of a direct injection engine according to a second embodiment of the present invention. , FIG. 6 is a control flowchart, FIG. 7 is a vertical sectional view of main parts of a direct injection engine according to the third embodiment of the present invention, and FIG. 9 is a vertical cross-sectional view of the main part of the direct injection engine according to the first modification of the direct injection engine shown in FIG. 7, and FIG. 1θ is IX in FIG. 9.
-IX main part arrow view, 1st! The figure is a vertical sectional view of the main part of the direct injection engine according to the second female example of the direct injection engine shown in Fig. 7, FIG. 12 is a xn-xn main part arrow view of FIG. FIG. 7 is a vertical cross-sectional view of main parts of a direct injection engine according to a third modification of the direct injection engine shown in FIG.
Fig. 3 is a XIV-XIV main part arrow view, Fig. 15 is a control area diagram of the direct injection engine shown in Fig. 7, and Fig. 16 is a time chart diagram of the ignition system of the direct injection engine shown in Fig. 7. ,
17 is a control flowchart of the direct injection engine shown in FIG. 7, FIG. 18 is a time chart of the ignition system in the direct injection engine according to the fourth embodiment of the present invention, and FIG.
FIG. 9 is a control flowchart, FIG. 20 is a correlation diagram between fuel injection amount and glow plug surface temperature, and FIG. 21 is a time chart of an ignition system in a direct injection engine according to a fifth embodiment of the present invention. FIG. 22 is a control characteristic diagram of a spark plug, FIG. 23 is a control flowchart diagram, and FIG. 24 is a load-fuel consumption characteristic diagram of a diesel engine. ! ...Cylinder 2 ...Cylinder head 3 ...Piston 4 ...Cavity 5 ...Fuel injection valve 6 ...Glow plug 7 ...・Spark plug 1! ...Intake boat 12...Exhaust boat Fig. 9 Fig. 10 Fig. 4 Fig. 18 Fig. S ÷ - Low - → High engine Fig. 24

Claims (1)

[Claims] 1. A direct injection engine in which an auxiliary ignition means is provided facing a cavity of the engine, and the fuel injected into the cavity is combusted by the auxiliary ignition means,
The auxiliary ignition means includes a glow plug and a spark plug, and the spark plug is selectively activated in a low engine load range, and the glow plug is selectively activated in a high engine load range. A direct injection engine.