JPH04370343A - Idle rotation speed control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To properly control and increase an engine speed while stably holding stratified combustion at the time of cold-state idle operation of a 2-cycle engine by adding an idle correction amount to a basic fuel injection amount to calculate fuel injection time. CONSTITUTION:A target engine speed setting means 58 in accordance with a water temperature, a deviation calculating means 59 for calculating a deviation between a target speed and an engine speed, an idle correction amount calculating means 60 for calculating an idle correction amount corresponding to the deviation at the time of idle operation and a fuel injection time calculating means 56 for calculating fuel injection time by adding an idle correction amount to a basic fuel amount are provided. At the time of idle operation, the idle correction amount is calculated corresponding to the deviation between the target speed in accordance with a water temperature and the engine speed to increase only fuel corrected with a fixed intake air amount by the idle correction amount, and thus at cold time, stratified combustion is well held to feedback-control the engine speed so as to properly rise, to promote warming up and further to stabilize rotation.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an idle speed control device for a two-stroke vehicle engine that controls the fuel injection amount and combustion method according to operating conditions. This relates to feedback control of rotation speed.

0002

[Prior Art] 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 during the compression stroke after the piston closes the scavenging port and before ignition. do. At high loads, the timing of fuel injection is determined early to achieve uniform combustion.
The applicant has already proposed a method in which the combustion method is changed to perform stratified combustion at a slower rate during idle and low and medium loads, and in addition to this change in combustion method, the combustion injection amount is controlled to control load operation. There is. At idle and under low load, the intake air volume is set constant and only the fuel injection volume is varied to control the load in order to perform stratified combustion well and improve operational stability. . Incidentally, even in such a two-stroke engine, it is desirable to appropriately increase the engine speed during idling operation when the water temperature is low to promote warm-up and avoid instability due to increased friction.

Conventionally, regarding the idle control during the cold state, there is a prior art technique disclosed in, for example, Japanese Unexamined Patent Publication No. 1-232133. Here, it is shown that the lower the water temperature is, the larger the initial fuel increase value is set, the amount of fuel supplied to the engine is increased based on this initial value, and then the increase value is gradually decreased.

0004

[Problems to be Solved by the Invention] By the way, in the prior art described above, the amount of fuel injection is increased or decreased along with the amount of intake air during cold idling operation of a 4-stroke engine. When adapted to this, there are problems such as the state of stratified combustion fluctuating in response to changes in the amount of intake air, making it difficult to maintain combustion in a stable state during cold conditions. Therefore, during cold idling operation of a two-stroke engine, it is necessary to perform different control from that of a four-stroke engine.

The present invention has been made in view of this point, and during cold idling operation of a two-stroke engine,
The purpose is to appropriately increase and control the engine speed while stably maintaining stratified combustion.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention determines the combustion method depending on the operating conditions, controls fuel injection and ignition timing for stratified combustion at least at low and medium loads, and uniformly controls the fuel injection and ignition timing at high loads. In a control system that controls fuel injection and ignition timing for combustion, a target rotation speed setting means sets a target rotation speed according to water temperature, a deviation calculation means calculates a deviation between the target rotation speed and the engine rotation speed, and an idle The system includes an idle correction amount calculation means for calculating an idle correction amount corresponding to a deviation during driving, and a fuel injection time calculation means for calculating a fuel injection time by adding the idle correction amount to the basic fuel injection amount.

[0007]

[Operation] Based on the above configuration, when a two-stroke engine is idling, the idle correction amount is calculated in response to the deviation between the target rotation speed according to the water temperature and the engine rotation speed, and the idle correction amount is used to maintain a constant intake air. Only the amount of fuel is corrected by increasing the amount of fuel, and as a result, feedback control is performed to properly maintain stratified combustion and increase the engine speed appropriately when the engine is cold.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. In FIG. 2, to explain the overall structure of a two-stroke direct injection gasoline engine, reference numeral 1 is the main body of the two-stroke engine, and a piston 3 is installed in the cylinder 2.
is inserted so as to be able to reciprocate, and the crankshaft 5 of the crank chamber 4
The piston 3 is connected by a connecting rod 6 provided eccentrically with respect to the crankshaft 5, and a balancer 7 is provided on the crankshaft 5 so as to offset the reciprocating inertia force of the piston 3. Combustion chamber 8
has an offset, wedge, or semicylindrical shape, and a high-pressure single-fluid injector 10 is installed at a high position near the center top.
is installed so that it is 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 10 in the injection direction.

The distance between the injector 10 and the electrode 9a is
It is set in consideration of the cone-shaped fuel spray that is injected just before ignition at low and 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 rear 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 is opened in the cylinder 2 and is opened and closed at a predetermined timing by a piston 3. A catalyst device 13 and a muffler 14 are connected to an exhaust pipe 12 from the exhaust port 11.
is provided. Here, an exhaust rotary valve 15 is installed in the exhaust port 11, and is connected to the crankshaft 5 by a belt means 16 to individually determine opening and closing of the exhaust port 11. That is, when the piston 3 begins to rise from the bottom dead center side, the exhaust port 11 is closed early by the exhaust rotary valve 15, making it possible to set the timing of fuel injection earlier in the uniform combustion method under high load. There is.

[0011] Furthermore, in the cylinder 2, the exhaust port 1
A scavenging port 17, which is similarly opened and closed by the piston 3 at a predetermined timing, is provided at a position shifted by 180 degrees or about 90 degrees in the circumferential direction with respect to the scavenging port 17. The air cleaner 19 is connected to the intake pipe 18 of the scavenging port 17.
A throttle valve 20 is provided which opens according to the opening degree of the accelerator, and a scavenging pump 21 is connected to the crankshaft 5 by a belt means 22 downstream of the throttle valve 20, and is constantly driven by the engine power to generate scavenging pressure. established in Here, the throttle valve 20 is set to open slightly even when the accelerator is fully closed, allowing the scavenging pump 21 to take in suction.
0 opens to control the amount of air. The scavenging pressure of air alone is used to forcefully scavenge air, supplying air with high filling efficiency.

To explain the high pressure fuel system of the injector 10, a fuel tank 30 communicates with the injector 10 via a fuel passage 35 having a filter 31, a fuel pump 32, a fuel pressure regulator 33, and an accumulator 34 for absorbing pressure fluctuations. A return passage 36 from the fuel pressure regulator 33 communicates with the fuel tank 30. The fuel pressure regulator 33 then 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 under 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.

Referring to FIG. 1, a fuel injection and ignition timing control system will be described as an electronic control system. First, the crank angle sensor 40, the cylinder discrimination sensor 41, the idle switch 42, the accelerator opening sensor 43 that detects the accelerator opening α, the vehicle speed sensor 44 that detects the vehicle speed V, the fuel pressure sensor 45 that detects the fuel pressure Pf, and the water temperature Tw. It has a water temperature sensor 46 for detection, and these sensor signals are input to a control unit 50.

The control unit 50 includes a crank angle sensor 4
It has an engine rotation speed detection unit 51 that inputs a crank angle of 0, and detects the engine rotation speed N depending on the crank pulse time etc.
Detect e. Signals from the crank angle sensor 40 and the cylinder discrimination sensor 41 are input to a crank position detection section 52, which detects the reference position before the top dead center of each cylinder. Engine speed N
e and the accelerator opening α are input to the basic fuel injection amount search unit 53, and the basic fuel injection amount Gfs corresponding to each driving condition is searched and determined from a map of the basic fuel injection amount Gfs with respect to Ne and α. The fuel pressure Pf is input to the fuel pressure constant setting section 54 and the injector invalid injection time setting section 55, respectively, and the fuel pressure constant K and the injector invalid injection time Ts are set with interpolation calculations using a grid table set in advance for the fuel pressure Pf. , these basic fuel injection quantities Gfs, fuel pressure constants K,
The injector invalid injection time Ts is determined by the fuel injection time calculation unit 5.
Enter 6.

The idle control system has an idle determination section 57 that receives the signal from the idle switch 42 and the vehicle speed V, and determines whether the vehicle is idling when an idle ON signal is input when the vehicle is stopped. It has a target rotation speed setting section 58 into which the water temperature Tw is input, and sets an appropriate target rotation speed Ned for the water temperature Tw. Here, Fig. 3 (a
), when the water temperature is below a predetermined set value Tws, the lower the water temperature Tw is, the higher the target rotation speed Ned becomes.
seek. This target rotation speed Ned and engine rotation speed Ne
is input to the deviation calculating section 59, and the deviation ΔN is calculated as the target rotation speed N.
It is calculated by subtracting the engine speed Ne from ed, and this deviation ΔN and the idle determination signal are input to the idle correction amount calculation section 60. The idle correction amount calculation unit 60 calculates the idle correction amount Gfa for the deviation ΔN during idle,
Calculate as follows.

That is, the idle correction amount Gfa is set as follows using the proportional feedback value P and the integral feedback value I. Gfa=P+I Therefore, the proportional feedback value P is set to P=Kp·ΔN using a constant Kp, and the constant Kp is determined as a function of ΔN. The constant Kp is set by experiment so that the rotation speed fluctuation is minimized,
As shown in FIG. 3B, when the actual value is smaller than the target value, the constant Kp is determined by a positive increasing function, and when the actual value is larger, the constant Kp is determined by a negative increasing function. Further, the integral feedback value I is set as I=Io+Ki·ΔN using the constant Ki and the previous integral feedback value Io, and the constant Ki is similarly determined as a function of ΔN. In this way, the feedback value P of these proportional and integral components,
I adjusts the idle correction amount G to compensate for the deviation ΔN with less fluctuation depending on the size and state of the deviation ΔN.
fa is determined, and this idle correction amount Gfa is input to the fuel injection time calculation section 56. The fuel injection time calculation unit 56 calculates the fuel injection time Ti from the basic fuel injection amount Gfs, the fuel pressure constant K, the injector invalid injection time Ts, and the idle correction amount Gfa as follows. Ti=K(Gfs+Gfa)+Ts

On the other hand, the basic fuel injection amount Gfs is input to a fuel injection timing determining section 61, an ignition timing determining section 62, and a combustion method determining section 63. In the combustion method determination unit 63, the switching point between the stratified combustion method and the uniform combustion method is set in advance using the Ne-Gfs map, and the injection amount set value Gfo at this switching point is compared with the basic fuel injection amount Gfs, and the・Gfs for medium load
＜Gfo, stratified combustion is performed, and high load Gfs≧Gfo
Uniform combustion is determined in this case, and this determination signal is output to the fuel injection timing determining section 61 and the ignition timing determining section 62.

The fuel injection timing determining unit 61 has a map of fuel injection timings θie and θis for each stratified combustion method and uniform combustion method based on the engine speed Ne and the basic fuel injection amount Gfs. In the case of uniform combustion, the fuel injection timing θis of the uniform combustion method is searched on a map and output. Here, in stratified combustion, it is necessary to end injection with a predetermined atomization time left immediately before ignition, so in this case, the injection end timing θie is set. on the other hand,
In uniform combustion, it is necessary to start injection early after the exhaust gas closes, so in this case, the injection start timing θis is set. The ignition timing determining section 62 also determines the engine rotation speed Ne.
It has a map of the ignition timing θg for each combustion method based on the basic fuel injection amount Gfs and the basic fuel injection amount Gfs, and searches the map for the ignition timing θg for each combustion method.In this way, stratified combustion occurs at low and medium loads, and uniform combustion occurs at high loads. It is designed to burn.

The fuel injection time Ti and the fuel injection timing θie or θis are input to the fuel injection timing setting section 64,
The drive unit 6 sends an injection signal according to the fuel injection time Ti and the fuel injection timing θie or θis based on the crank angle reference position.
5 to operate the injector 10. The ignition timing θg is inputted to the ignition timing setting section 66, which outputs ignition signals such as ignition timing and dwell time according to the ignition timing θg to the drive section 67 to operate the spark plug 9. configured to allow

Next, the operation of this embodiment will be explained. First, during engine operation, the throttle valve 20 opens according 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 11 opens, and then the scavenging port When 17 is also opened, this pressurized air flows into the cylinder 2 from the scavenging port 17. Then, due to the vertical swirl flow of this supply air, the cylinder 2
Scavenging is performed to push out residual gas from the exhaust port 11 and 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 port 17
closes and moves 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 Pf is controlled by the fuel pressure regulator 33 according to the operating conditions, and this fuel is guided to the injector 10.

Further, in the control unit 50, the basic fuel injection amount search section 53 searches a map for the basic fuel injection amount Gfs according to the engine speed Ne and the accelerator opening degree α, and further searches for the fuel pressure constant K, according to the fuel pressure Pf. An injector invalid injection time Ts is set. Therefore, under operating conditions other than idling, the fuel injection time calculation section 56 calculates the fuel injection time Ti based on the basic fuel injection amount Gfs, and at the same time, the combustion method determination section 63 determines the combustion method, and the fuel injection timing determination section 61, the map of the ignition timing determining section 62 is selected based on this determination.

Therefore, at low and medium loads, the fuel injection timing determining section 61 selects the stratified combustion map, and thereby the fuel injection timing θie is determined to be close to the ignition timing, and the ignition timing determining section 62 also selects the stratified combustion map. The ignition timing θg
is determined relatively close to top dead center. Then, by outputting an injection signal to the injector 10 based on the fuel injection time Ti and the fuel injection timing θie, a relatively small amount of fuel is injected toward the electrode 9a of the spark plug 9 in the late stage of compression, and immediately after that, the injection signal based on the ignition timing θie is output to the injector 10. An ignition signal is output to the ignition plug 9. For this reason, before the cone-shaped fuel spray diffuses, it is ignited by the electrode 9a at its rear end, resulting in stratified combustion.In this way, even if the fuel is very small compared to the amount of air, a rich mixture of fuel can be effectively used. Stable combustion is achieved using this method.

[0023] Also, at high load, the basic fuel injection amount Gfs
As the number increases, a map for the uniform combustion method is selected by the fuel injection timing determining section 61 and the ignition timing determining section 62. Therefore, the ignition timing θg is determined to be the optimum value when the fuel injection timing θis is early after the exhaust rotary valve 15 is closed, and therefore a large amount of fuel is injected from the injector 10 into the cylinder 2 at the beginning of compression. , fuel and air are thoroughly mixed during compression. After this uniform mixing, the spark plug 9 ignites the mixture, resulting in uniform combustion with a high air utilization rate, increasing engine output.

Next, the idle operation will be explained using the flowchart of FIG. First, in step S1, engine rotation speed Ne, water temperature Tw, vehicle speed V, accelerator opening degree α
, fuel pressure Pf, and idle switch signal are read, and in step S2, the basic fuel injection amount Gfs is searched using a map of engine speed Ne and accelerator opening α.In step S3, idling is determined based on the idle switch signal and vehicle speed V. Therefore, in the case of the driving operation state, the process proceeds to step S4, where the idle correction amount Gfa is set to zero,
In step S5, the fuel injection time Ti is calculated based only on the basic fuel injection amount Gfs, and this signal is output and controlled as described above.

On the other hand, if it is determined that the engine is idling while stopped, the process proceeds to step S6, and the target rotation speed Ned is set to the water temperature T.
Therefore, the target rotational speed Ned is set high according to the map shown in FIG. 3(a) in the cold state. After that, in step S7, the deviation ΔN between the target rotational speed Ned and the engine rotational speed Ne is calculated, and in step S8
In step S9, the proportional and integral feedback value constants Kp and Ki corresponding to this deviation ΔN are searched, and in step S9, the proportional and integral feedback values P and I are calculated. The idle correction amount Gfa is calculated based on the feedback values P and I.

Therefore, when starting the engine, the
When the water temperature Tw is a low value Tw1, a correspondingly high target rotational speed Ned1 is set, so the idle correction amount Gfa is calculated to a large value Gfa1. Then, in step S5, the fuel injection time Ti is calculated to be larger by adding this idle correction amount Gfa1 to the basic fuel injection amount Gfs, and as a result, only the fuel is increased with respect to a constant intake air amount, and the stratified The engine speed Ne increases as the amount of fuel increases while maintaining good combustion. At this time, when the engine speed Ne increases or decreases with respect to the target speed Ned1, the idle correction amount Gfa1 is appropriately decreased or increased according to the feedback values P and I described above, and thus the engine speed The number Ne is feedback-controlled so as to maintain a state substantially equal to the target rotational speed Ned1 with little variation.

After that, when the water temperature Tw rises to Tw2 as shown in FIG. 5, the target rotational speed Ned slightly decreases to Ned2 and the idle correction amount Gfa is also reduced to Gfa2.
The engine rotational speed Ne is similarly controlled to decrease with respect to the target rotational speed Ned2 with little variation. In the same manner, the engine speed Ne is controlled to gradually decrease as the water temperature Tw increases, and warm-up is promoted by such high idle speed control, and the engine speed is reduced as the friction increases. The number Ne is kept stable. Then, when the water temperature Tw reaches the set value Tws,
The target rotational speed Ned is set to a predetermined idle rotational speed Nes, and therefore the idle correction amount Gfa becomes a value near zero, and the engine rotational speed Ne similarly reaches this predetermined idle rotational speed Nes with little fluctuation. It will be subject to constant control.

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

[0029]

[Effects of the Invention] As explained above, according to the present invention,
During idle operation in a 2-stroke engine, only the fuel is controlled to increase or decrease depending on the water temperature, so it is possible to control high idle speed while maintaining a good low-load stratified combustion condition. It can promote warm-up and prevent rotation from becoming unstable due to increased friction. Since the idle correction amount is calculated as a function of the deviation between the target rotational speed and the engine rotational speed using feedback values of the proportional and integral components and is corrected to increase, the idle rotational speed can be controlled with little rotational fluctuation. Since the target rotation speed is set for the water temperature and the engine rotation speed is feedback-controlled to this target rotation speed, fluctuations in the rotation speed due to factors such as friction can be reliably reduced, and the idle rotation speed after warming up can be reduced. can also be optimally controlled.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electronic control system showing an embodiment of an idle speed control device for a two-stroke engine according to the present invention.

FIG. 2 is a block diagram schematically showing the entire two-stroke engine of the present invention.

FIG. 3 shows control maps, in which (a) is a map of target rotation speed, and (b) is a map of feedback value constants.

FIG. 4 is a flowchart showing the effect of control during idling operation.

FIG. 5 is a diagram showing the operating state during cold idle operation.

[Explanation of symbols]

1 2-cycle engine body 9 Spark plug 10 Injector 50 control unit 53 Basic fuel injection amount search section 56 Fuel injection time calculation section 58 Target rotation speed setting section 59 Deviation calculation section 60 Idle correction amount calculation section 61 Fuel injection timing determination section 62 Ignition timing determination section 63 Combustion method determination section

Claims (2)

[Claims] Claim 1: A control system that determines a combustion method based on operating conditions, controls fuel injection and ignition timing for stratified combustion at least at low and medium loads, and controls fuel injection and ignition timing for uniform combustion at high loads, a target rotation speed setting means for setting a target rotation speed according to water temperature; a deviation calculation means for calculating a deviation between the target rotation speed and the engine rotation speed;
It is characterized by comprising an idle correction amount calculation means for calculating an idle correction amount corresponding to a deviation during idle operation, and a fuel injection time calculation means for calculating a fuel injection time by adding the idle correction amount to a basic fuel injection amount. Idle speed control device for 2-stroke engines. 2. The idle correction amount calculating means calculates the idle correction amount by calculating proportional and integral feedback values using at least a deviation and a constant corresponding to the deviation, and adding these feedback values. The idle speed control device for a two-stroke engine according to claim 1.