JP2843380B2 - Crankcase preload / fuel injection multi-cylinder two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a crank chamber preload type / fuel injection type in which fuel (gasoline or the like) is injected into an intake passage upstream of a combustion chamber and ignited by a spark plug. The present invention relates to a multi-cylinder two-cycle engine.

BACKGROUND OF THE INVENTION Two-cycle and four-cycle fuel injection engines are known in which fuel (gasoline or the like) is injected into intake air, a mixture is sucked into a combustion chamber, and ignited by a spark plug. In this type of conventional engine, the amount of intake air is detected by an air flow meter or the like, and the amount of fuel injection is controlled by the amount of intake air. Here, the injection amount is controlled by changing the valve opening time width of the injection valve. In this case, for example, during a low load operation in which the intake air amount is small, the valve opening time width of the injection valve must be sufficiently short. However, the injection valve has a controllable minimum injection time width, and it has not been possible to limit the injection amount below the injection amount corresponding to the minimum injection time width. Further, when the injection valve is used in the vicinity of the minimum injection time width, there is a problem that it is impossible to control the injection amount with high accuracy.

In addition, it is conceivable to use an injection valve having a sufficiently small minimum injection time width, but in this case, the control width of the injection amount of the injection valve becomes large, and the processing accuracy must be significantly increased, and the cost becomes high. Occurs.

(Object of the Invention) The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a crankcase preload / fuel injection type multi-cylinder two-cycle engine capable of controlling a small amount of injection with high accuracy without using a high-precision injection valve having a significantly small minimum injection time width. I do.

(Constitution of the Invention) According to the present invention, it is an object of the present invention to provide a multi-cylinder two-stroke engine with a preload / fuel injection type in which an intake pipe is separately connected to a crank chamber via a reed valve for each cylinder. A plurality of throttle valves separately provided in the intake pipe of each cylinder, a plurality of crank chamber pressure detecting means for separately detecting the crank chamber pressure of each cylinder, a plurality of fuel injection valves separately provided for each cylinder, A plurality of fuel pressure regulators that are separately provided for each cylinder and decrease the fuel pressure supplied to the fuel injection valve in accordance with an increase in the intake negative pressure in the intake pipe of each cylinder; and a fuel injection amount and an injection timing of each cylinder. A control device for controlling the control device, wherein the control device calculates an intake / intake amount using a crank chamber pressure of each cylinder, and in a predetermined operation state, sets a fuel injection valve of each cylinder to a predetermined value within one cycle of each cylinder. Taimin The engine is controlled by a regular injection method in which the injection amount is changed by changing the valve opening time width of each fuel injection valve in accordance with the intake air amount, while in other operating states, the number of cycles in a plurality of engine cycles is controlled. This is achieved by a crank chamber preload / fuel injection type multi-cylinder two-cycle engine characterized in that the fuel injection valve is opened by a smaller number of injections and the injection amount is controlled by the number of injections to perform a thinning injection system.

(Embodiment) FIG. 1 is an overall system diagram of one embodiment of the present invention, FIG. 2 is a diagram showing injection timing, and FIG. 3 is a control characteristic diagram of an injection amount M.

In FIG. 1, reference numeral 10 denotes a crankcase preload type two-cycle 2
This is a cylinder engine having two cylinders 12 and 14. Crank chambers 16 and 18 of the cylinders 12 and 14 are independently formed in one common crankcase. Reference numeral 20 denotes a crankshaft, and the piston of each cylinder is connected to the crankshaft 20 by a connecting rod.

Reference numeral 22 denotes an electric fuel pump, which is, for example, a roller pump, and supplies fuel from a fuel tank 24 to a fuel injection valve 40 described later.
To pump.

26 (26a, 26b) is a shutter type throttle valve.
The two throttle valves 26 are formed substantially symmetrically, and are connected to the crankcase by rubber joints 28 (28a, 28b). In addition, a reed valve is attached to a connection portion between the joint 28 and the crankcase. The joint 28 of each cylinder and the throttle body 30 (30a, 30b) of the throttle valve 26 form an intake pipe of each cylinder. A valve plate 32 (32a, 32b) is mounted on the throttle body 30 (30a, 30b) of each throttle valve 26 from above to be able to move up and down. Rotation of a throttle grip (not shown) provided on the steering handle is performed by levers 34 (34a, 34b),
Conveyed to valve plate 32 by link 36 (36a, 36b)
Raise and lower 32. The opening θ of the throttle valve 26 is determined by a potentiometer 38 attached to the right side of the right throttle valve 26b.
Is detected by

Each of the throttle bodies 30 is provided with an electromagnetic fuel injection valve 40 (40a, 40b), which injects fuel obliquely from the vicinity of the lower edge of the valve plate 32 toward the intake air flow direction. These fuel injection valves 40 are of a so-called bottom feed type, in which fuel is supplied to the injection port side from the electromagnetic coil from the side. Fuel injection valve 40 for both cylinders
The fuel pumped from the fuel pump 22 is distributed to the left and right by a delivery pipe.

Reference numerals 42 (42a, 42b) denote fuel pressure regulators, which control the fuel pressure fed from the fuel pump 22 to the injection valve 40 to each of the cylinders 12, 14
Is adjusted to a predetermined pressure determined by the intake negative pressure. That is, when the fuel pressure supplied from the fuel pump 22 to the injection valve 40 becomes equal to or higher than a predetermined pressure determined by the intake negative pressure, a part of the fuel is circulated to the fuel tank 24.

This regulator 42 has a diaphragm 44 (44a, 44b)
And an intake negative pressure chamber 46 defined by the diaphragm 44.
(46a, 46b) and a fuel pressure chamber 48 (48a, 48b). In the intake negative pressure chamber 46, a pipe 47 (47
a, 47b) guide the intake negative pressure. The fuel pressure chamber 48 is connected to a pipe connecting the fuel pump 22 and the injection valve 40, and the fuel pressure of the injection valve 40 is guided. Diaphragm 44
, A return force to the fuel pressure chamber 48 side is applied by a compression spring 50 (50a, 50b). Also, the diaphragm 44 has a fuel pressure chamber
The fuel pressure adjusting nozzles 52 (52a, 52b) face each other from within 48, and the diaphragm 44 becomes a flapper that approaches and separates from the nozzle 52, thereby forming a known flapper-nozzle type pressure adjusting mechanism.

Therefore, when the fuel pressure increases beyond a predetermined value, the pressure in the fuel pressure chamber 48 increases, and the diaphragm 44 compresses the spring 50 to displace and open the nozzle 52. Here, since the intake negative pressure is guided to the negative pressure chamber 46, when the intake negative pressure increases, the fuel pressure at which the nozzle 52 starts to open decreases.

In general, when the load is low, the fuel injection time becomes extremely short, and there is a case where the injection amount cannot be controlled only by the injection time due to the limit of the responsiveness of the fuel injection valve 40. According to this embodiment, in this case, the number of injections of the fuel injection valve 40 is thinned out (thinning injection method) as described later, while the injection amount is reduced by lowering the fuel pressure.
It is not necessary to increase the responsiveness of the fuel cell, and highly accurate control can be performed without using an expensive fuel injection valve. Also, when the throttle valve 26 is closed rapidly during high-speed operation, the fuel injection amount also sharply decreases, and the fuel pressure temporarily rises. However, according to this embodiment, the fuel pressure regulator 42 detects the intake negative pressure. As a result, the fuel pressure is quickly released, so that the injection amount can always be accurately controlled. In this way, the diaphragm 44 is
When the fuel is released from the nozzle 52 while compressing the fuel, the fuel in the fuel pressure chamber 48 is returned from the nozzle 52 to the fuel tank 22. Note that the two fuel pressure regulators 42 are both mounted on the outer surface of the throttle body 30 and are close to the fuel injection valve 40, so that the injection pressure can be controlled with high accuracy.

Reference numeral 54 (54a, 54b) denotes a pressure detector as a crank chamber pressure detecting means for detecting the internal pressure of the crank chambers 16, 18, and is attached to the vehicle body frame via a rubber tamper. These pressure detectors 54 are connected to the left and right outer surfaces of the crankcase by pipes 56 (56a, 56b), detect the internal pressure of the crank chambers 16, 18, and output electric signals p _a , p _b corresponding to the internal pressures. I do.

The pipe 56 has an air check valve 58 (58a, 5
8b) is attached (Fig. 1). This check valve 58
Is a pressure detector that allows only outside air to flow into the pipe 56.
The mixture in the crank chambers 16 and 18 is prevented from flowing into 54.

60 is the rotational speed N of the crankshaft 20 and the ignition timing signal α
Is a rotation speed detector for detecting the rotation speed.

Reference numeral 62 denotes a control device constituted by a microcomputer. The control device 62 receives signals such as the throttle opening θ, the crank chamber pressures p _a and p _b , the rotation speed N, and the ignition timing signal α. Also, the control may be performed by inputting various signals such as the engine temperature T, other engine acceleration / deceleration, and engine brake.

The control device 62 determines the optimum fuel injection amount M corresponding to the operating state based on these various input signals, obtains the injection time for the injection amount M, and opens the solenoid valve of the fuel injection valve 40. Here, the control device 62 has a memory 62A built therein, and the characteristics of the optimum injection amount M shown in FIG. 3 are stored in advance in this memory 62A in the form of an arithmetic expression or a map, and the injection amount M is obtained.

In a predetermined operating state, for example, during a high / medium load operation, the injection amount M is large and the injection time width t is long, so that the injection valve 40 can follow the opening / closing timing, and one cycle of the engine (one rotation of the crankshaft in a two-cycle engine) One or more intermittent injections are made at a fixed timing within two revolutions in a four-cycle engine) (periodic injection). FIG. 2A shows that at a predetermined timing within one cycle β of the engine,
The state in which the injection of the injection time widths t ₁ , t _2, ...

Here, the control characteristic of the optimum injection amount M will be described with reference to FIG. FIG. 3 shows the optimum injection amount M with respect to the rotation speed N and the crankcase pressure P. In FIG. 3, hatched portions ABCD and ABEF indicate correction amounts depending on temperature, air pressure, etc., and GHILKL portions indicate a low speed rotation range. Shows the increase in weight. This increase in the low-speed rotation range is suitable for increasing the engine output (low-speed torque) at a low speed to obtain an engine output characteristic particularly suitable for a trial competition. Furthermore, the MNOPQR part is for high-speed, high-load operation, and the STU part is for high-speed, low-load operation to reduce the injection amount to improve fuel efficiency.

On the other hand, during a low-load operation in which the throttle valve opening θ is less than one constant (θ ₀ ), the injection time determined by the control device 62 is short. In the present embodiment, during a low-load operation in which the throttle valve opening θ is an opening smaller than θ ₀ , the injection frequency n is set in a range higher than the idling speed N _{ad and} higher than the speed N ₀ , that is, in a region surrounded by abcdUSTF. Injection is performed thinning out without corresponding to one cycle of the engine.

2B and 2C show such a situation. That is, the number of injections n in the χ cycle of the engine is set to n <χ. Here is obtained by regular intervals the injection interval and the injection time width t constant t ₀ in the embodiment of Fig. 2 B, this time the injection time width t may also be variable at the same time according to the intake air amount . In the embodiment of FIG. 2C, the injection is stopped once every two cycles, thinned out, and the injection time width t is changed to t ₁ , t _2, ... In accordance with the injection amount M.

In this embodiment, the rotational speed of the engine and the crank angle α are detected by one common rotational speed detecting means 54, but these may be detected by separate detectors.

(Effect of the Invention) As described above, the present invention provides a fuel pressure regulator for each cylinder and separately controls the fuel pressure supplied to the fuel injection valve of each cylinder in accordance with the intake negative pressure in the intake pipe of each cylinder. On the other hand, the intake air amount is detected using the crank chamber pressure detected separately for each cylinder, and in a predetermined operation state, each fuel injection valve is controlled by a regular injection method, and in other operation states, by a thinning injection method. Since the control is performed, it is possible to control the minute injection amount with high accuracy without making the injection port of the injection valve too small. Therefore, it is not necessary to use an expensive injection valve. Also, since the fuel pressure regulator controls the fuel pressure for each cylinder, detects the intake air amount using the crank chamber pressure of each cylinder, and controls the injection amount of each fuel injection valve,
It is possible to accurately control the injection amount of each cylinder.
Further, since the fuel is injected into the intake pipe of each cylinder, mixing of the fuel and the intake can be promoted by using a large volume of the space in the intake pipe and the space in the crank chamber. Averaging enables smooth operation.

[Brief description of the drawings]

1 is an overall system diagram of one embodiment of the present invention, FIG. 2 is a diagram showing injection timing, and FIG. 3 is a control characteristic diagram of an injection amount M. 10, a two-stroke two-cylinder engine, 16, 18, a crankcase, 28 a joint forming a part of an intake pipe, 30 a throttle body forming a part of an intake pipe, 40 a fuel injection valve , 42 ... Fuel pressure regulator, 54 ... Pressure detector as crank chamber pressure detecting means, 62 ... Control device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00 F02M 69/00 340

Claims (1)

(57) [Claims] In a crankcase preload / fuel injection type multi-cylinder two-cycle engine in which an intake pipe is separately connected to a crank chamber via a reed valve for each cylinder, the intake pipe is provided separately for each cylinder. A plurality of throttle valves, a plurality of crank chamber pressure detecting means for separately detecting the crank chamber pressure of each cylinder, a plurality of fuel injection valves separately provided for each cylinder, and a plurality of fuel injection valves separately provided for each cylinder. A plurality of fuel pressure regulators for lowering the fuel pressure supplied to the fuel injection valves in accordance with an increase in the intake negative pressure in the intake pipe of each cylinder; and a control device for controlling a fuel injection amount and an injection timing of each cylinder, The control device calculates the intake air amount using the crank chamber pressure of each cylinder, and in a predetermined operating state, opens the fuel injection valve of each cylinder at a predetermined timing in one cycle of each cylinder, and according to the intake air amount. The fuel injection is controlled by a regular injection method in which the injection amount is changed by changing the valve opening time width of each fuel injection valve. A multi-cylinder two-stroke engine with a crank chamber preload and fuel injection, characterized in that the valve is opened and controlled by a thinning injection method in which the injection amount is changed according to the number of injections.