JPH0412153A - Controller of two cycle engine - Google Patents

Abstract

PURPOSE:To obtain torque characteristics which correspond to load and decrease fuel consumption by controlling operation in such a manner as switching a combustion type so that layered combustion takes place in low/middle load, uniform combustion take place in high load, intermittent combustion takes place in low load with a specified engine speed or more. CONSTITUTION:In a control unit 50, acting as a control system during fuel injection and ignition timing, a fuel injection pulse width calculation unit 53 is provided, and a fuel injection quantity Gf is map-retrieved according to an engine operation condition. A fuel injection type judgement unit 56 is provided and engine speed Ne gives a standard of judgement whether the present combustion is intermittent combustion of load with more than the specified engine speed or more, layered combustion in low/middle load, or uniform combustion in high load. The judgement signal is inputted to a fuel injection timing setting unit 54, and to an ignition timing determining unit 55. Fuel injection timing map and ignition timing map are selected per combustion type in each case, and proper fuel injection timing and proper ignition timing are determined and outputted. The judgement signal of the combustion type judgement unit 56 is inputted together to the intermission times setting unit 57, and intermission times is determined at the time of intermittent combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for controlling a fuel injection amount and a combustion method according to operating conditions in a two-stroke engine for a vehicle.

[Conventional technology]

Generally, an injector is installed in the combustion chamber of a two-stroke vehicle engine, and fuel is injected directly into the cylinder at high pressure at least during the compression stroke after the exhaust system is closed and before ignition.

The applicant has already proposed an in-cylinder direct injection system in which the timing of fuel injection is set early to achieve uniform combustion, and the timing of fuel injection is set late to achieve stratified combustion.

In the above-mentioned in-cylinder direct injection two-stroke engine, a scavenging pump is installed in the air supply system to efficiently perform scavenging, an exhaust rotary valve is installed in the exhaust system to expand the fuel injection area, and the electrodes of the injector and spark plug are installed. A technical idea has been disclosed for optimizing the positional relationship between the two to achieve stratified combustion at low and medium loads and uniform combustion at high loads. Here, it is desired to perform control so as to smoothly shift to the stratified combustion method at low/medium loads and the uniform combustion method at high loads.

Therefore, conventionally, regarding the control system of this type of engine that controls both fuel injection and combustion method, for example,
There is a prior art of Publication No. 36719. Here, it has been shown that when the load is low, stratified combustion occurs through in-cylinder direct injection, and when the load exceeds a predetermined load, uniform combustion is achieved by dispersing and supplying fuel using the injection nostle in the intake system.

[Invention or problem to be solved]

By the way, in the prior art described above, the intake air amount is determined to be constant during stratified combustion at low load, and in-cylinder injection is performed by the injection nozzle. It cannot be applied to combustible items.

At low and medium loads in the medium and high speed ranges, the fuel pressure increases, which increases the fuel injection amount, and the engine torque becomes more than the torque commensurate with the load, causing the torque characteristics to change based on the combustion method that corresponds to the load. It is difficult for connections to transition smoothly,
In this respect, proper load control is required to maintain good combustion at all times.

The present invention has been made in view of the above points, and its purpose is to provide a two-stroke engine capable of optimally controlling combustion and load over a wide range from idling to high load, thereby achieving smooth torque characteristics. The purpose of this invention is to provide a control device.

[Failure to solve the problem]

In order to achieve the above object, the two-stroke engine control device of the present invention employs stratified combustion at low and medium loads in the control system of an in-cylinder direct injection two-stroke engine that controls the load by switching the combustion method depending on the operating conditions. , combustion method determining means for determining uniform combustion at high loads and thinning combustion at low loads at or above a predetermined engine speed; and combustion method determination means for determining fuel t・1 injection timing 8 ignition timing for each combustion method by determining the combustion method. Fuel injection timing determination stage 1 ignition timing determination means that outputs fuel injection timing by searching the map, decimation number setting means that outputs a combustion signal according to the number of culling times during culling combustion, fuel injection pulse width, fuel injection of each combustion method The fuel injection timing setting means outputs a fuel injection signal in response to the delayed combustion signal.

[For production]

Based on the above configuration, in a 2-stroke engine, the thinning combustion method is determined at low loads above a predetermined engine speed,
In this case, the fuel injection timing is 1 ignition timing, and a small amount of fuel is injected just before ignition once every few times according to the combustion signal, resulting in good stratified combustion and torque characteristics commensurate with the load. Also, at low and medium loads, the combustion switches to stratified charge combustion, and at high loads, the combustion switches to uniform combustion, maintaining good combustion while continuously changing the torque characteristics.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 2, the overall configuration of a two-stroke direct injection gasoline engine is described. Reference numeral 1 is the main body of the two-stroke engine, in which a piston 3 is inserted into a cylinder 2 so as to be able to reciprocate, and a crank in a crank chamber 4 is inserted. The piston 3 is connected by a connecting rod 6 provided eccentrically with respect to the shaft 5, and a balancer 7 is provided on the crankshaft 5 so as to offset the reciprocating inertia force of the piston 3. The combustion chamber 8 has a hemispherical, wedge, or semicylindrical shape, and a high-pressure single-fluid injector 10 is installed at a high position near the top of the center so as to be open for the ON time (pulse width) of the pulse signal. Further, the spark plug 9 is installed at an angle so that the electrode 9a is located directly below the injector IO in the injection direction.

The distance between the injector 10 and the electrode 9a is set in consideration of the cone-shaped fuel spray that is injected just before ignition at low/medium loads. That is, when the distance is short, atomization is insufficient, and when the distance is long, the spray diffuses, so that between the two, the trailing end of the spray can be ignited and stratified combustion can occur. In addition, since the injector 10 is arranged approximately on the center line of the cylinder 2, a large amount of fuel injected at an early stage under high load quickly diffuses throughout the cylinder 2 from its internal center and is uniformly premixed. This makes it possible to burn evenly.

An exhaust port 11 that opens and closes at a predetermined timing by a piston 3 is opened in the cylinder 2, and a catalyst device 13. A muffler I4 is provided.

Here, an exhaust rotary valve 15 is installed in the exhaust port [1], and is connected to the crankshaft 5 by a belt means I6 to individually determine the opening and closing of the exhaust port 11. That is, when the piston 3 rises, the exhaust port [+ is closed early by the exhaust rotary valve 15 on the bottom dead center side, making it possible to set the timing of fuel injection earlier in the uniform combustion method under high load. .

In addition, in the cylinder 2, on the F dead center side from the exhaust port 11, at positions shifted approximately 180 degrees and 90 degrees in the circumferential direction,
Similarly, a scavenging port 17 is opened and provided, which is opened and closed by the piston 3 at a predetermined timing. An air cleaner 19. A throttle valve 20 that opens according to the accelerator opening is provided, and a scavenging pump 21 or a belt means 22 is provided downstream of the throttle valve 20.
The pump is connected to the crankshaft 5 by the pump, and the pump is always driven by the engine power to generate scavenging pressure. Here, the throttle valve 20 is set to open slightly even when the accelerator is fully opened, allowing suction by the scavenging pump 21, and when this play range is exceeded, the throttle valve 20 opens in accordance with the accelerator opening to control the amount of air. The scavenging pressure of air alone is used to forcefully scavenge air, supplying air with high filling efficiency.

That is, the throttle opening φ' is set to have a nonlinear characteristic as shown in FIG. 3(a) with respect to the accelerator opening φ, and therefore the charged air amount Ga also has a nonlinear characteristic as shown in FIG. 3(b). become. In this way, good combustion is ensured as well as scavenging by the scavenging pump 21 even during idling with the accelerator released.

Regarding the high pressure fuel system of the injector lO, the fuel tank 30 is connected to the filter 31. Fuel pump 32, fuel pressure regulator 33. Accumulator 3 absorbs pressure fluctuations
4, a return passage 36 from the fuel pressure regulator 33 communicates with the fuel tank 30. and fuel pressure regulator 3
3 adjusts the return of high-pressure fuel from the fuel pump 32 to control the fuel pressure of the injector 10. Here, when the amount of charged air is small at low load, the fuel pressure is low, and when the amount of filled air increases due to an increase in load, the fuel pressure is also controlled to be high.

Next, in FIG. 1, a fuel injection 1 ignition timing control system will be described as an electronic control system.

First, the crank angle sensor 40. It has a cylinder discrimination sensor 41 and an accelerator opening sensor 42, and these sensor signals are input to the control unit 50. The control unit 50 has an engine rotation speed detection section 51 that manually detects the crank angle θ of the crank angle sensor 40, and detects the engine rotation speed Ne based on the time of the crank pulse.

Crank angle sensor 40. The signal from the cylinder discrimination sensor 41 is input to a crank position detection section 52, which detects the reference position before the top dead center of each cylinder.

Further, the fuel injection pulse width calculation unit 5 inputs the engine rotation speed Ne and the accelerator opening degree φ of the accelerator opening degree sensor 42.
3, and the fuel injection amount Gf is searched on the map according to each operating condition according to the engine speed Ne and the accelerator opening φ (7).Here, when the engine speed Ne is constant, the fuel injection amount Gf is It is set proportionally to the accelerator opening φ as shown in Fig. 3 (C), and due to this and the characteristics of the charged air amount Ga shown in Fig. 3 (b), the torque characteristics are set proportionally to the accelerator opening φ regardless of the combustion method. It can be increased or decreased depending on the opening degree φ.

In addition, as a determining factor of the fuel injection pulse width, the fuel injection @
In addition to Gf, there is fuel pressure Pf. In particular, the fuel pressure Pf is controlled separately from the high-pressure fuel system and the air supply system, and when the fuel pressure Pf is high, the amount of fuel is increased even with the same fuel injection pulse width. There, fuel pressure P
The correction coefficient K for f is set as a decreasing function. In this way, the fuel injection pulse width Ti is determined by the fuel injection iGf and the correction coefficient of 1. and the voltage correction numerator s, it is calculated as follows.

Ti - to -G f +Ts Next, the engine speed NO of each driving condition element.

The fuel injection jtGf is divided into stratified, stratified and uniform combustion methods including thinning. and is input to the combustion method determining section 56.

The fuel injection method determination unit 56 determines low-load thinning combustion, low/medium-load stratified combustion, and high-load uniform combustion when the engine rotational speed Ne is equal to or higher than a predetermined rotational speed. Here, the amount of charged air obtained from the maximum torque characteristic of each combustion method when the engine rotation speed Ne is a certain - constant rotation speed is expressed as follows.
X, Y in figure (a).

The torque characteristic when the fuel injection amount Gf is changed with the accelerator fully open is as shown in FIG. 4(b).

As a result, in uniform combustion, the characteristics shown by the solid line X are obtained with respect to the charged air amount Ga at which the maximum torque can be obtained with respect to the fuel injection amount Gf, and the characteristics of the flammability limit in this case are shown by the dashed-dotted line 2'. The maximum torque of stratified combustion is obtained by the amount of charged air shown by the solid line Y, and the flammability limit is the dashed line 2'.
The maximum torque of thinning combustion is obtained with the amount of charged air indicated by the solid line Z, and the flammability limit is indicated by the dashed-dotted line 2'. The operation line based on the relationship between the charged air amount Ga and the fuel injection tGf for the operation of the accelerator opening degree φ from fully closed to fully open is shown by a thick solid line.

Therefore, the fuel injection amount Gf at the switching point C between thinning and stratified combustion methods and the switching point C2 between stratified and uniform combustion methods,
, Gf2 are set in advance using a map as shown in FIG. 5(a). The switching points C, , C2 are shown in Fig. 4 (
The characteristics are set as shown by the dotted line C in a). Therefore, the combustion method determination unit 56 compares the fuel injection amount IGf, , Gf2 at the point at which the combustion method is changed based on the map of FIG.
When ≦Gf, thinning combustion is performed, and when Gf<Gf≦Gf2
Stratified combustion is determined when Gf2≦Gf, and uniform combustion is determined when Gf2≦Gf. This determination signal is input to the fuel injection timing determining section 541 and the ignition timing determining section 55.

The fuel injection timing determination unit 54 has a fuel injection timing map for each combustion method, and selects this map based on the combustion method determination signal to determine the optimal fuel injection timing according to the engine speed Nc and the fuel injection amount Gf. Output a signal. In stratified charge combustion, it is necessary to leave a predetermined atomization time before ignition to finish the injection, so in this combustion method, as shown in Figure 5 (C),
The optimal fuel injection start timing θiE is set. In uniform combustion, it is necessary to start injection early after the V[silver system closes, so in this case, the optimal fuel injection start timing θ1s is set as shown in FIG. 5(d). On the other hand, in thinning combustion, the fuel injection amount Gf is small, resulting in a combustion method similar to stratified combustion, but the optimal fuel injection timing θ1e when thinning out once every few times is set as shown in Figure 5 (b). . thus,
In the maps of these combustion methods, the fuel injection timing θte,
By outputting θiE or θis, the combustion method is essentially switched.

The ignition timing determination unit 55 determines and determines the optimum ignition timing θg. Here, engine speed NQ and fuel injection amount G
Depending on f, one optimum ignition timing θg is determined, or if the combustion method is different, the ignition timing θg will be different for each combustion method. Therefore, Fig. 5 (b), (c) =
As shown in (d), the ignition timing θg is set separately on the map for each of the thinning, stratified, and uniform combustion methods, and thus the optimum ignition timing θg is output for each combustion method.

The determination signal from the combustion method t11 fixed section 56 is further inputted to a thinning number setting section 57 to determine the number of thinnings during thinning combustion. For example, in the case of a 4-cylinder engine, as shown in Fig. 5(e), it is determined that stratified combustion is performed once every three times in each cylinder and as a whole, and fuel is cut off the remaining two times. Outputs the combustion signal once.

The above fuel injection pulse width Ti, fuel injection timing θicθtE
Alternatively, θis and the thinned-out combustion signal are input to the fuel injection timing setting section 58. Based on the crank angle reference position, the fuel injection pulse width Ti and the fuel injection timing θ are determined based on the crank angle reference position.
A fuel injection signal corresponding to iE or θis is outputted to the injector 10 via the drive unit 59 every cycle. On the other hand, during thinning combustion when the fuel injection timing θic is input, a fuel injection signal based on the fuel injection pulse width Ti and the fuel injection timing θic is output in synchronization with the combustion signal.

The ignition timing θg is input to the ignition timing setting section 60, and the ignition timing θg is configured to output ignition signals such as ignition timing and toll time to the spark plug 9 via the drive section 61 based on the crank angle reference position. be done.

Next, let's talk about the operation of the control device for a two-stroke engine with this configuration.

First, during engine operation, the throttle valve 20 opens in response to the accelerator opening and air is sucked into the scavenging pump 21 to generate a predetermined scavenging pressure.When the piston 3 descends, the exhaust port l+ opens, and then the scavenging air is When the boat 17 is also opened, this pressurized air flows into the cylinder 2 through the scavenging port 17. This vertical swirl flow of the supply air pushes out the residual gas in the cylinder 2 from the exhaust hole 11, and performs a scavenging action to fill the supply air with high filling efficiency. On the other hand, when the piston 3 begins to rise from the bottom dead center, the exhaust rotary valve 15 closes and scavenging ends, making it possible to inject fuel without causing fuel blow-through, and then the scavenging valve 17 closes. , and move on to the compression stroke. On the other hand, at this time, in the high-pressure fuel system of the injector 10, the fuel pressure is controlled by the fuel pressure regulator 33 according to the operating conditions, and this fuel is supplied to the injector 10.
guided by.

Further, the fuel injection pulse width output section 53 of the control unit 50
Then, the fuel injection amount Gf is searched on the map according to the engine speed Ne and the accelerator opening degree φ, and the fuel injection amount Gf is also searched.
The fuel injection pulse width Ti is calculated based on . At the same time, the combustion method determining section 56 determines the combustion method, and the map of the fuel injection timing determining section 541 and the ignition timing determining section 55 is selected based on this determination.

Therefore, when the engine speed is low load above the predetermined speed, 1
For example, the engine speed Ne shown in FIG. 5(a) is N
e2 or more, and when the accelerator opening φ is a predetermined opening, the combustion method determination unit 56 compares the required fuel injection MGf with the fuel injection @G f at the switching point C1, and determines that Gf≦Gf.
When , thinning combustion is determined. Therefore, the fuel injection timing determining section 54 selects the thinning combustion map shown in FIG. 5(b) to determine the fuel injection timing θie immediately before the ignition timing, and the ignition timing determining section 55 selects the thinning combustion map shown in FIG. 5(e). The optimum ignition timing θg of the thinning combustion method is searched on a map, and the thinning number setting section 57 outputs a combustion signal once every three times.

And these fuel injection pulse width Ti, fuel injection timing θ
1e, or the fuel injection timing setting unit 58 outputs the combustion signal to the injector 10 in synchronization with the combustion signal. Therefore, as shown in FIG. 6(a), just before ignition, a small amount of fuel or It is injected toward the electrode 9a of the plug 9. Then, the rear end of the fuel t4 spray is ignited by the electrode 9a, and in this way, the fuel is thinned out once every three times to perform stratified combustion. In this stratified combustion method, the throttle valve 20
is opened, sufficient scavenging is performed by the scavenging pump 2I, and the amount of charged air ff1Ga is relatively large, resulting in good combustion. Therefore, the torque characteristics during thinning combustion are as shown in Fig. 4(b) - (
c) The torque curve T1 shown in (d) has a low and gradually changing characteristic.

Next, when the load increases while the accelerator opening degree φ is constant, the fuel injection amount Gf increases, and when the fuel injection amount Gf at the switching point C1 becomes larger at low/medium load, stratified combustion is determined. Therefore, the fuel injection timing determination unit 54 selects the stratified combustion map, and thereby the fuel injection timing θ
iE is determined to be close to the ignition timing, and the ignition timing determining section 55
However, the optimum ignition timing θg is determined relatively close to top dead center by the stratified combustion map. and fuel injection pulse width Tf
.

Since the injection signal based on the fuel injection timing θie is output to the injector IO every cycle, a relatively small amount of fuel is injected toward the electrode 9a of the spark plug 9 in the late stage of compression, as shown in FIG. 6(b). , immediately after that, an ignition signal based on the ignition timing θg is output to the spark plug 9. For this reason, before the cone-shaped fuel spray diffuses, it is ignited by the electrode 9a at its rear end and switches to stratified combustion.In this way, even if the fuel is very small compared to the amount of air, a rich mixture of fuel is created. Stable stratified combustion is carried out by making effective use of this.

In such stratified charge combustion, the charging air amount Ga, the fuel injection @Gf
increases and is further burned each time, as shown in Figure 4(b),
Torque increases as shown in torque curve T2 shown in (c) and (d). In the case of thinning and because of the combustion method, the torque curve T1 smoothly transitions to the torque curve T2.

Furthermore, the fuel injection amount Gf or the fuel injection amount Gf2 at the switching point C2
At the time of high load increased above, uniform combustion is determined.

Therefore, the fuel injection timing determining section 541 and the ignition timing determining section 55 select a map for the uniform combustion method, and the fuel injection timing θi
The ignition timing θg is determined to be the optimum value at an early stage after the exhaust rotary valve 15 is closed. Therefore, as shown in FIG. 6(C), a large amount of fuel is injected into the cylinder 2 from the injector IO at the beginning of compression, and the fuel and air are sufficiently mixed during compression. After this uniform mixing, the spark plug 9 ignites and switches to uniform combustion. In such a uniform combustion method, a large amount of fuel is burnt satisfactorily with a high air utilization rate, and the torque further increases as shown by the torque curve T3 in FIGS. 4(b), (c), and (d). Also, switching point C
2, the set value Gf2 is set so that the torque of the stratified combustion method and that of the uniform combustion method are equal, so there is a smooth transition from the torque curve T2 to T3.

Note that when the accelerator opening degree φ decreases and the fuel injection ff1Gf decreases, the combustion method is switched, contrary to the above case, and the engine torque changes smoothly in accordance with the combustion method at switching points C2 and C.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto.

〔Effect of the invention〕

As described above, according to the present invention, in a two-cycle direct injection engine, stratified combustion occurs at low and medium loads, uniform combustion occurs at high loads, and thinned combustion occurs at low loads above a predetermined engine speed. Since the combustion method is controlled to switch and operate, especially at low loads above a predetermined engine speed, thinning combustion is performed, so torque characteristics corresponding to the load can be obtained, and fuel consumption can be reduced. There are also few.

Furthermore, when the load is low, the throttle valve is set to sufficiently scavenge air between the predetermined opening degrees, and stratified combustion is performed with high charging efficiency, so stable combustion occurs at low load, resulting in high torque. The characteristics can be adjusted to H77.

Furthermore, since the combustion method of low-load thinning combustion and stratified combustion is interstitial combustion, the combustion and torque characteristics are continuously switched.

In addition, the switching points of thinning, stratified, and uniform combustion methods are set so that the torque characteristics match the engine speed and fuel injection amount, so the overall torque characteristics change continuously. Become.

Furthermore, by setting the fuel injection timing and ignition timing for each combustion method, each combustion can be performed optimally.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electronic control system showing an embodiment of a control device for a two-cycle engine according to the present invention, and FIG.
Figure 3 (a) to C) is a diagram showing various characteristics, Figure 4 is a torque characteristic diagram of thinning, stratified, and uniform combustion methods, Figure 5 (a) ) or d) is the fuel injection amount for each combustion method,
A diagram showing a map of fuel injection timing and ignition timing. (e) is a diagram showing the thinned combustion state in the case of 4 cylinders,
The figure is a diagram showing fuel injection states of each combustion method. 1... 2-cycle engine body, 9... Spark plug, 10... Injector, 50... Control unit, 5
3... Fuel injection pulse width calculation unit, 54... Fuel injection timing determination unit, 55...-Ignition timing determination unit, 56... Combustion method determination unit, 57... Thinning number setting unit, 58.・
Fuel injection timing setting unit patent applicant: Fuji Heavy Industries Co., Ltd. #1 Agent: Nobu Kobashi, patent attorney

Claims (6)

[Claims] (1) In the control system of a direct injection two-stroke engine, which controls the load by switching the combustion method depending on operating conditions, stratified combustion is performed at low and medium loads, uniform combustion is performed at high loads, and combustion is performed at low and Combustion method determining means for determining thinning combustion for each load; fuel injection timing determining means and ignition timing determining means for searching a map and outputting fuel injection timing and ignition timing for each combustion method based on combustion method determination; A thinning number setting means for outputting a combustion signal according to the number of times of thinning during thinning combustion; a fuel injection timing setting means for outputting a fuel injection signal according to the fuel injection pulse width, the fuel injection timing of each combustion method, and the thinning combustion signal. A two-stroke engine control device comprising: (2) The combustion method determining means determines the switching point between the thinned stratified, stratified and uniform combustion methods so that the torque matches the fuel injection amount at each engine speed, and determines the fuel injection amount under the operating condition at the switching point. 2. The two-stroke engine control device according to claim 1, wherein the combustion method is determined by comparing the combustion method with the combustion method. (3) The fuel injection timing determination means determines the fuel injection timing for each combustion method using a map of engine speed and fuel injection amount, and determines the fuel injection timing immediately before ignition for thinning and stratified combustion, and immediately after exhaust system closure for uniform combustion. 2. The two-stroke engine control device according to claim 1, wherein: (4) The fuel injection timing setting means is characterized in that it outputs a fuel injection signal based on the fuel injection pulse width and fuel injection timing every cycle in stratified combustion and uniform combustion, and in synchronization with the combustion signal in thinning combustion. 2 of claim (1)
Cycle engine control device. (5) A two-stroke engine according to claim (1), characterized in that a throttle valve is disposed upstream of the scavenging pump in the air supply system, and the throttle valve is set to be opened by a predetermined amount near the opening of the accelerator. Control device. (6) The fuel injection pulse width of the two-stroke engine according to claim (1) is characterized in that the fuel injection amount is determined based on the accelerator opening degree and the engine speed, and is calculated using a coefficient depending on the fuel pressure. Control device.