JPH04132876A - Fuel injection device for two-cycle engine - Google Patents

Abstract

PURPOSE:To improve startability and stability of idling operation by effecting injection of fuel only through an auxiliary fuel injection valve when a fuel pressure is lower than a main pressure value necessary to a main fuel injection valve. CONSTITUTION:In a two-cycle engine 1, a fuel injection device 10 is provided with a main fuel injection valve 11 to inject fuel directly in a cylinder and an auxiliary fuel injection valve 16 to inject and feed fuel to a suction passage 12 communicated to a crank chamber 2a. In which case, when a fuel pressure is lower than a main pressure value necessary to the main fuel injection valve 11, fuel is injected only through the auxiliary injection valve 16. For example, during the starting of an engine 1, a time in which a fuel pressure is boosted to an auxiliary pressure value, namely a time until the starting of injection is shortened. A time in which the engine 1 is started can be shortened by the time until the starting of the engine, and startability is improved. For example, even when a main pressure value is reduced due to deterioration with time of a fuel pump 26, a fuel injection amount is stabilized and idling operation is stabilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises a main fuel injection valve that injects fuel directly into a cylinder, and an auxiliary fuel injection valve that injects fuel into an intake passage communicating with a crank chamber. The present invention relates to a fuel injection device for a two-stroke engine equipped with a fuel injection system, and particularly relates to an improved fuel injection method that can shorten the time required to start the engine and improve stability during idling.

[Conventional technology]

The cylinder-injection 2-stroke engine injects fuel directly into the cylinder to purify exhaust gas.

It is advantageous in improving fuel efficiency and output, and has recently attracted attention from this point of view.

This type of engine is equipped with a mechanical fuel pump that boosts the pressure of fuel to a pressure that can be injected against the cylinder white compression pressure, and a mechanical air pump that generates compressed air to perform the fuel injection well. It is common that

When starting the engine, both pumps are rotated by the starter motor, and when the fuel and air reach a predetermined pressure, they are injected into the cylinders and ignited.

[Problem to be solved by the invention]

However, the two-stroke engine equipped with the conventional fuel injection device has the problem that it takes time to start the engine, and if the discharge pressure capacity of the pump decreases due to aging etc., idling may become unstable. There is.

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to shorten the time required to start the engine and improve startability, and even if the pump deteriorates over time, idling operation becomes unstable. The object of the present invention is to provide a fuel injection device for a two-stroke engine that does not cause

[Means to solve the problem]

The present inventors investigated the cause of the long startup time and the cause of unstable idling, and found the following points. When injecting fuel with a fuel injection device, high fuel pressure is required to overcome the compression pressure within the cylinder. However, it takes a certain amount of time to raise the fuel pressure to the required main pressure value, especially with a mechanical pump.
As a result, startability is poor due to the time required for this pressure increase.

Furthermore, if the discharge pressure becomes unstable due to deterioration of the fuel pump or the like over time, the amount of fuel injected by the fuel injection device becomes unstable, resulting in unstable idling. In addition, to solve this problem, it would be good to have enough pump capacity, but in the case of motorcycles in particular, it is difficult to use a large-capacity pump due to the installation space and large output loss. be.

On the other hand, this type of engine tends to run out of fuel in certain operating ranges, such as at high speeds and high loads. In addition to the valve, some models are equipped with an auxiliary fuel injection valve that injects fuel into the intake passage communicating with the crank chamber in a predetermined high-speed, high-load operating range. The present invention was developed by focusing on the fact that since the fuel is injected into the intake pipe, the fuel is injected at a lower pressure than the main fuel injection valve.

Therefore, the present invention provides a fuel injection device for a two-cycle engine that includes a main fuel injection valve that injects fuel directly into a cylinder, and an auxiliary fuel injection valve that injects fuel into an intake passage that communicates with the crank chamber. The present invention is characterized in that when the fuel pressure is lower than the main pressure value required for the main fuel injection valve, injection is performed only by the auxiliary fuel injection valve.

Here, an example of a case where the fuel pressure is lower than the main pressure value required for the main fuel injection valve is, for example, when starting the engine, the rotation speed of the starter motor is low, so the rotation speed of the fuel pump is also low, and therefore the fuel pressure is low. There may be cases where the fuel pressure does not reach the main pressure value, or where the fuel pressure is lower than the main pressure value because the rotational speed of the engine itself is low, such as during idling.

[Effect]

According to the fuel injection device for a two-stroke engine according to the present invention, when the fuel pressure is lower than the main pressure value required for the main fuel injection valve, fuel injection is performed by the auxiliary fuel injection valve; The auxiliary pressure value required for the fuel injection valve is much lower than the above main pressure value. Therefore, for example, when starting an engine, the time it takes for the fuel pressure to rise to the auxiliary pressure value, that is, the time until injection starts. As a result, the time required to start the engine can be shortened accordingly, and startability can be improved.

In addition, if the fuel pressure becomes unstable when the engine speed is low, such as when idling, due to aging of the pump, for example, and drops below the main pressure value, fuel injection is performed only by the auxiliary fuel injection valve. The fuel injection amount does not become unstable, so idling operation becomes stable. In this case, there is no need to provide sufficient capacity for the fuel pump.

〔Example〕

1 and 2 are diagrams for explaining a fuel injection device for a two-stroke engine according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a direct injection type two-stroke two-cylinder engine equipped with the device of this embodiment.
and connect the piston 6 inserted into the cylinder body 3 with the connecting rod 7 to the crank arm 9 of the crankshaft 9.
It has a structure connected to a. Combustion recess 4 recessed in the upper surface of the piston 6 and the lower surface of the cylinder head 4
Combustion chamber 5 is constituted by a. The crank arm 9a is housed in a crank chamber 2a of the crank case 2, and the crank chamber 2a communicates with the cylinder bore via a scavenging road 3a formed in the cylinder body 3.

A spark plug 8 is mounted on the cylinder head 4 with its electrode portion facing into the combustion chamber 5. A fuel injection device 10 is mounted on the cylinder head 4, and an injection nozzle lla of a main fuel injection valve 11 of the fuel injection device 10 faces into the combustion chamber 5 near the spark plug 8. Further, the main fuel injection valve 11 has a fuel rail 11b.

Air rail llc is connected.

Here, the direct injection engine to which the present invention is directed is characterized by performing so-called stratified charge combustion in which a combustible mixture cloud is formed in a combustion chamber, and the cloud is ignited and combusted.

However, the required ignition timing of the air-fuel mixture for performing such combustion is very delicate and unstable. In other words, the ignition timing is determined by the engine speed, throttle opening, etc. in a normal two-stroke engine. On the other hand, in a direct injection engine, it is necessary to ignite when the air/fuel ratio in the air-fuel mixture cloud reaches approximately 14 (appropriate timing), but such appropriate timing varies for each engine or operating state. Therefore, it is difficult to ignite at the above timing.

Therefore, in the ignition system of the engine of this embodiment, by making the time during which current flows through the ignition coil at each engine speed, that is, the on-time, be as long as possible, the instability of the above-mentioned appropriate timing is absorbed, and the ignition of the air-fuel mixture is I try to have as many opportunities as possible to do so.

3 and 4 are a crank angle-on-time characteristic diagram and an engine rotation speed-on-time characteristic diagram, respectively. In this example, as shown in FIG. 3, from the opening of the exhaust port to near the end of fuel injection The crank angle is set to allow on-time, and the remaining crank angle is set to allow discharge, and the on-time and discharge timing are set within this range. However, as shown in Figure 4, it is preferable to gradually shorten the on-time when the engine speed exceeds a certain value, or to maintain the on-time at a predetermined value in the high-speed rotation range, as shown by the broken line. This makes it possible to prevent coil burnout and reduce power consumption.

Further, an intake passage 12 is connected to the crankcase 2 and communicates with the crank chamber 2a.
An air cleaner 13 is connected to the upstream end of the engine, and a gate valve 14 is installed at a portion facing the crank chamber 2a. Further, a throttle valve 15 is disposed upstream of the reed valve 14 in the intake passage 12, and the amount of intake air is adjusted by the opening degree of the throttle valve 15. Further, an auxiliary fuel injection valve 16 is installed between the throttle valve 15 and the reed valve 14, and an injection nozzle 16 of the injection valve 16 is installed.
faces the crank chamber 2a.

One end of the crankshaft 9 projects outward from the crankcase 2, and a reduction gear 20 is fixed to the projecting portion. This reduction gear 20 has a pair of drive gears 21.
22 are connected to each other, and a near compressor 24 is connected to one of the drive gears 21 via a one-way clutch 23.

Further, the other drive gear 22 includes a one-way clutch 25.
A fuel pump 26 is connected via.

Furthermore, the starter motor 2 is connected to both the clutches 23 and 25.
The starter gears 27 of No. 8 are in mesh with each other, so that the starter motor 28 is connected to the crankshaft 9 at the time of starting.
and the near compressor 24.
The fuel pump 26 is driven and is released after the engine 1 is started. The suction port of the fuel pump 26 is connected to the fuel tank 3 through a fuel filter 30a by a fuel hose 3o.
1, and its discharge port is connected to the fuel rail Ilb by a high-pressure fuel passage 33 via a Pulsera silane damper 33a and a pressure accumulator 33b.

Further, an air filter 24a is connected to the suction port of the near compressor 24, and a discharge port is connected to the air rail Ilc by a high pressure air passage 32. Furthermore, the fuel and air rail 11b.

A main regulator 35' is connected to the downstream side of 11c. This main regulator 35 is for maintaining the fuel pressure at a main pressure value that is necessary for main fuel injection and is higher than air pressure by a certain differential pressure. Further, the secondary fuel is supplied to the auxiliary fuel injection valve 1 through the low pressure fuel passage 36.
6, and the secondary air is exhausted to an exhaust pipe or canister.

Further, the secondary side of the auxiliary fuel injection valve 16 is connected to the fuel tank 31 by a fuel return pipe 37 via an auxiliary regulator 38 . This sub-regulator 38 is for adjusting the fuel pressure to a sub-pressure value passed through sub-fuel injection.

50 is a controller that controls fuel injection of the engine 1, and this controller is connected to a cooling water temperature sensor 51.50 disposed in the cylinder head 4. A crank angle sensor 52 disposed on the other end of the crankshaft 9, a crank chamber pressure sensor 53 disposed in the intake passage 12. Above throttle valve 1
Throttle opening sensor 54 disposed at 5. Detection values from each sensor of the intake air temperature sensor 55 disposed in the air cleaner 13 are input, and the main fuel injection valve 11. It is configured to control the injection timing and injection amount of the auxiliary fuel injection valve 16, and to drive and control the electromagnetic oil pump 40 and the like.

Although not shown, the controller 50 includes a first CPU for angle synchronization processing and a second CPU for time synchronization processing.
It has a built-in U. The first CPU receives the detected value from the crank chamber pressure sensor 53 in synchronization with the detected value from the crank angle sensor 52, and the second CPU receives the detected value from the throttle opening sensor 54 and other sensors in time synchronization. is input. Then, fuel injection is controlled by interfering the calculated value of the first CPU with the second CPU.

Next, the effects of this embodiment will be explained.

When starting the engine 1 of this embodiment, the starter motor 2
8, the crankshaft 9 is driven by the motor 28, and the near compressor 24.8 is turned on. The fuel pump 26 is driven, thereby increasing the pressure of air and fuel and supplying it to the air rail 11C0 and the fuel rail llb.

When these pressures reach the auxiliary pressure value required for the auxiliary fuel injection valve 16, the auxiliary fuel injection valve 16 injects fuel into the intake passage 12.
The resulting air-fuel mixture is supplied from the crank chamber to the combustion chamber, and is ignited at a predetermined timing to start the engine 1. When the fuel pressure reaches the main pressure value required for the main fuel injection valve 11, the injection is switched to the main fuel injection valve 11. In this case, if the fuel pressure has already reached the main fuel injection pressure from the beginning, such as at the time of restart, fuel is immediately injected from the main fuel injection valve 11 without injecting from the auxiliary fuel injection valve 16. .

The operation of the fuel injection device of this embodiment will be further explained in detail along the flowchart of FIG.

First, when the ignition switch is turned on, the controller 50 sequentially reads the detection values from each sensor and initializes each data (step S1). Then, when the starter motor 28 is rotated, the crankshaft drive of the motor 28 causes the controller 50 to initialize the data. Read the engine rotation speed (cranking rotation speed) and check that the rotation speed N is 11000≧N≦30Orpm.
It is determined whether the rotation speed is within the range (steps S2 and S3), and if the rotation speed is outside the above range, it is determined that the engine is unable to start.
Return to step S1. If the rotation speed is within the above range, it is determined that the engine is ready to start, the fuel pressure is read, and it is determined whether or not this fuel pressure is higher than 5.5 kg/- (steps S4 and S5). Furthermore, the fuel pressure is 2.5
Step S6) to determine whether it is higher than kg/-;
If this fuel pressure is lower than 2.51 tr/-, the process returns to step S2. If the fuel pressure becomes higher than 2.5 kg/-, fuel injection is performed by the auxiliary fuel injection valve 16. In this case, the throttle angle (opening degree) and crank chamber pressure are read (steps S7 and S8). , map the fuel injection amount and injection timing corresponding to these data and the engine speed read in step S2 (step S9), and inject the above amount of fuel into the intake passage 12 at the above timing using the auxiliary fuel injection valve 16. Inject.

The engine 1 is started by igniting the air-fuel mixture formed by this fuel injection at a predetermined timing.

Next, the engine is started by injection from the auxiliary fuel injection valve 16, and when the fuel pressure reaches 5.5 ka=/cd, the process shifts to main fuel injection from step S5.

In this case, throttle angle, crank chamber pressure.

and the fuel injection amount and timing according to the engine rotation speed are calculated from the main fuel injection MAP, and the main fuel injection valve 11 injects based on the calculated values (step 5ll-3
14), here, regarding the transition to the main fuel injection, the engine speed is a predetermined idling speed (for example, 13
5Orpm), the transition may be made.

In addition, even after the engine has started, the discharge capacity decreases due to aging of the pump, for example, and the engine speed is low, such as during idling, so the fuel pressure may become lower than the main pressure value (5.5 kg/cj). If it has decreased, in steps 86 to SIO, the auxiliary fuel injector 1
Fuel is injected from 6.

It should be noted that a force (not shown) is applied to the auxiliary fuel in addition to the main fuel injector 11 even if the fuel pressure is higher than the main pressure value, in high-speed rotation and high load areas where the engine speed and throttle angle are above a predetermined value. Fuel is also injected and supplied from the injection valve 16.

As described above, according to the engine 1 of this embodiment, the fuel pressure is 2.5 kg/esl (secondary pressure value) when the engine is started.
Since fuel injection is started by the auxiliary fuel injection valve 41 when the fuel temperature becomes higher, the time until the start of fuel injection, that is, the time required to start the engine, is shortened accordingly, and startability can be improved. Also, after starting the engine, the fuel pressure is 5.
When the fuel injector reaches 5 kg/-, the main fuel injection valve 11 is used, so there is no problem in normal operation.

Further, during idling, if the fuel pressure falls below the main pressure value, fuel is injected by the auxiliary fuel injection valve 16. Therefore, even if the fuel pump has a reduced discharge capacity due to deterioration over time, the fuel injection amount during idling can be stabilized, and the idling rotation speed can be stabilized.

Furthermore, in this embodiment, processes synchronized with the crank angle, such as the crank chamber pressure, are performed by the first CPU, and processes synchronized with time, such as the throttle opening, are performed by the second CPU.

Eliminates complexity when configuring software.

Incidentally, in the conventional device, the crank chamber pressure is converted into time-synchronized processing using a signal hold circuit and processed by the same CPU, but in this case, a decrease in accuracy of the crank angle due to the above conversion is unavoidable. In the direct injection two-stroke engine to which the present invention is directed, injection timing is extremely important, and the decrease in accuracy described above tends to be an obstacle to improving engine performance. However, as in this embodiment, angle synchronization processing and time synchronization The above problem can be solved by performing the processing using separate CPUs.

In the embodiment described above, the auxiliary fuel injection valve injects fuel into the intake pipe at startup. On the other hand, in the direct injection engine targeted by the present invention, the throttle opening is set relatively large even at low speeds.
If intake pipe injection is performed at startup, a large amount of fuel will be supplied corresponding to the large opening of the throttle valve, and there is a risk that the engine speed will become excessive immediately after startup. To solve this problem, it is desirable to inject from the auxiliary fuel injection valve and retard the ignition timing at the time of startup.

Further, in the above embodiment, in order to stabilize the idling speed, fuel is injected only from the auxiliary fuel injection valve when the fuel pressure is lower than the main pressure value. By the way, in order to set the above-mentioned idling speed low, it is necessary to control the fuel injection amount very minutely, so even if the above-mentioned embodiment method is adopted, the fuel injection valve is required to have an extremely wide dynamic range. . On the other hand, there is a limit to the expansion of the dynamic range. To solve this problem, it is conceivable to perform a thinning operation during idling operation. As a result, there is no need to reduce the fuel injection amount so much, and the dynamic range also does not need to be so large. A method of stopping fuel injection can be adopted. In addition,
In this case, it goes without saying that the total injection amount for a certain period of time is set to be the same as when no thinning is performed.

〔Effect of the invention〕

As described above, according to the fuel injection device for a two-stroke engine according to the present invention, fuel injection is performed only by the auxiliary fuel injection valve when the fuel pressure is lower than the main pressure value. This has the effect of shortening the time and improving startability, as well as stabilizing idling operation.

[Brief explanation of the drawing]

1 to 4 are diagrams for explaining a fuel injection device for a two-stroke engine according to an embodiment of the present invention,
Fig. 1 is a schematic diagram of the engine according to the embodiment, Fig. 2 is a flowchart for explaining the operation of the fuel injection device, Fig. 3 is a crank angle-on time characteristic diagram, and Fig. 4 is an engine speed-on-time characteristic diagram. It is an on-time characteristic diagram. In the figure, 1 is a two-stroke engine, 2a is a crank chamber, 30a is a main fuel injection valve, 35 is an intake passage, and 41 is an auxiliary fuel injection valve. Patent Applicant Yamaha Motor Co., Ltd. Agent Patent Attorney Tsutomu Shimofu Figure 3

Claims (1)

[Claims] (1) In a fuel injection system for a two-stroke engine that is equipped with a main fuel injection valve that injects fuel directly into a cylinder and an auxiliary fuel injection valve that injects fuel into an intake passage that communicates with the crank chamber, the fuel pressure A fuel injection device for a two-cycle engine, characterized in that when the main pressure value is lower than the main pressure value required for the main fuel injection valve, fuel injection is performed only by the auxiliary fuel injection valve.