JPH0264239A - Engine braking device for two cycle direct injection engine - Google Patents

Abstract

PURPOSE:To prevent fuel from being blown-by as well as to enable engine braking efficiency to be suitably controlled by cutting off fuel from an injector at the time of deceleration while the footing stroke of an accelerator pedal is kept less than a specified one, and thereby concurrently controlling a pressure reducing valve. CONSTITUTION:In a two cycle direct injection engine, an engine main body 1 is provided with an injector 10 for injecting fuel into a combustion chamber 8, and with a pressure reducing valve 61 for functioning decompression on the combustion chamber 8 side. The pressure reducing valve 61 is provided with an actuator 64 which opens/closes the pressure reducing valve 61 based on electrical signals from a control unit 45. This situation permits fuel from the injector 10 to be cut off at the time of deceleration while the footing stroke of an accelerator pedal is kept less than a specified one. This concurrently permits engine braking force to be maximum at the time of fully closing the accelerator pedal, and also permits the pressure reducing valve 61 to be controlled in such a way that engine braking force is gradually reduced in changing the valve opening depending on the footing stroke of the accelerator pedal. This constitution therefore prevents fuel from being blown-by, thereby allowing engine braking efficiency to be smoothly lowered as the footing stroke of the accelerator pedal is made greater.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an engine braking device for a two-stroke direct injection engine in which fuel is directly injected into a cylinder by an injector, and more particularly to measures to enhance the engine braking effect by decompression and fuel cut.

[Conventional technology]

Generally, in a 2-cycle engine, one cycle ends with one revolution of the crankshaft, so compared to a 4-stroke engine, which ends one cycle with two revolutions of the crankshaft and has an intake stroke. The drawback is that there is little pump work and the engine brake is not very effective. Therefore, in a vehicle driven by a two-stroke engine, it is necessary to be equipped with means for enhancing the engine braking effect when the accelerator is released. Conventionally, there is a prior art technique, for example, disclosed in Japanese Patent Application Laid-Open No. 61-272425, regarding countermeasures against engine braking for the two-stroke engine. Here, a first valve is provided in the combustion chamber, and the valve is opened by rotating the handle grip further from the idle position in the direction of closing the throttle valve. It is also shown that a low-return valve whose opening area changes depending on the engine speed is provided in the communication passage.

[Problem to be solved by the invention]

By the way, in the prior art described above, since the decompression amount is determined by the engine speed immediately before deceleration, the control is constant, so the effectiveness of the engine brake is made constant, which is not preferable. Also, there is no mention of fuel supply during decompression, but in this case, the compression pressure drops and combustion becomes impossible, and the fuel is discharged as is, worsening emissions, so it is necessary to prevent this. The present invention has been made in view of the above points, and its purpose is to prevent fuel blow-through in an engine brake strengthening method using decompression, and to provide a two-cycle system that can optimally control the engine brake effect. An object of the present invention is to provide an engine braking device for a direct injection engine.

[Means to solve the problem]

In order to achieve the above object, the engine braking device of the present invention is a two-stroke direct injection engine in which an injector for injecting fuel is attached to the combustion chamber of the two-stroke engine main body, and a pressure reducing valve for decompression is attached to the combustion chamber side.
The pressure reducing valve is provided with an actuator that opens and closes the pressure reducing valve based on an electric signal from a control unit, and cuts the fuel from the injector when the accelerator pedal is depressed below a predetermined amount when decelerating while the vehicle is running, and at the same time opens and closes the pressure reducing valve. The engine braking force is maximized when the accelerator is fully closed, and the opening degree is controlled so as to gradually reduce the engine braking force in accordance with the amount of accelerator depression.

[For production]

Based on the above configuration, fuel from the injector is cut off when the accelerator pedal is depressed less than a predetermined amount during deceleration while the vehicle is running, thereby preventing fuel from blowing through. At this time, when the accelerator is fully closed, the decompression effect by the pressure reducing valve is greatly controlled, producing a large engine braking effect due to the pump's workload, and as the amount of accelerator depression increases, the decompression effect gradually decreases depending on the opening degree of the pressure reducing valve. Then, the engine braking effect decreases smoothly, and the engine returns to self-destruction again.

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. In FIG. 1, to describe the overall structure of the two-stroke engine, reference numeral l is the main body of the two-stroke engine, in which a piston 3 is inserted into the cylinder 2 so as to be able to move back and forth, and is connected to the crankshaft 5 of the crank chamber 4. The piston 3 is connected by an eccentric connecting rod B, and a balancer 7 is provided on the crankshaft 5 so as to offset the reciprocating inertia of the piston 3. A spark plug 9 and an in-cylinder direct injection type injector IO are attached to the top of the combustion chamber 8. 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 an exhaust chamber 14.t are connected to the exhaust pipe 12 communicating with the exhaust pipe 12. A muffler 15 is provided. In addition, a scavenging boat 16 that opens and closes at a predetermined timing by the piston 3 opens at a position approximately 90 degrees away from the position of the exhaust port 11 of the cylinder 2 (or a position facing the exhaust port 11). A scavenging system is installed. The injector 10 is of a two-fluid type, which stores a predetermined amount of fuel and then presses it with pressurized air to directly inject the fuel and air in a mixed state. Therefore, the fuel passage 20 of the injector 10 is connected to the filter 2.
1. communicates with the fuel tank 23 via the fuel pump 22;
A pressure regulating valve 24 is provided in the middle of the fuel passage 20, and always produces a constant low fuel pressure (slightly higher pressure than the pressurized air). In addition, a pressure regulating valve 2 is provided in the air passage 25 of the injector 10.
6. Accumulator 27. The compressor 28 is connected,
It is designed to produce pressurized air. Then, a predetermined amount of fuel is stored in the injector 10 in advance by a fuel pulse, and after the exhaust port 11 is closed, pressurized air is applied to the fuel by an air pulse and the fuel is injected. Next, regarding the scavenging system of the scavenging port 1B, the scavenging pipe 30 communicating with the scavenging port 16 is connected to a displacement type via a scavenging chamber 31 that absorbs the scavenging pressure waves when the scavenging port 1B is opened and closed, and an intercooler 32 that cools the scavenging air. A scavenging pump 33 is installed in series. Further, a bypass passage 35 communicates between the air cleaner 34 side upstream of the scavenging pump 33 and the downstream side of the intercooler 32;
A control valve 36 for load control is provided. The scavenging pump 33 is connected to the crankshaft 5 by a transmission means 37, and the engine output constantly drives the pump to generate scavenging pressure. Regarding the control system, the accelerator pedal 40 is connected to the control valve 36 via an opening degree changing means 41 so that the opening degree of the control valve 36 is opened and closed in inverse proportion to the amount of accelerator depression. Also, an engine rotation speed sensor 42 that measures the engine rotation speed N and accelerator depression amount θ that determines each operating condition. It has an accelerator depression amount detection sensor 43. and engine speed sensor 42. Signals N and θ of accelerator depression amount detection sensor 43
is manually processed by the control unit 45, and the control unit 45 outputs fuel and air pulse signals to the injector 10 and ignition signals to the spark plug 9. On the other hand, as a measure to strengthen the engine brake, a pressure reducing passage 60 is connected from the combustion chamber 8 side of the cylinder 2 to the exhaust passage 11a of the exhaust port 11, and in this pressure reducing passage 60, a poppet valve type pressure reducing valve 61 has a return spring 62. The pressure reducing valve 61 is connected to a solenoid actuator 64 via a link mechanism 63. In response to an electric signal from the control unit 45, an actuator 64 opens and closes the pressure reducing valve 61 to perform decompression. The control unit 45 will be described in FIG. First, the engine rotation speed sensor 42. It has an operating condition detection section 46 which inputs the engine rotation speed N and accelerator depression 2θ of the accelerator depression amount detection sensor 43, and the signals of each operating condition Q are inputted to the cylinder air port calculation section 47 to determine the timing during scavenging. For the blowout, the actual in-cylinder air port is determined by taking into account the amount of air and the pressurized air port from the injector IO. This in-cylinder air amount signal is input to the fuel injection plate calculation unit 48, and the target air-fuel ratio setting unit 49
The fuel injection amount is determined in relation to the target air-fuel ratio, and pulse signals of fuel and air corresponding to this are output from the pulse output section 50 to the injector IO. The vehicle also has a deceleration detecting section 51 to which signals of various driving conditions are input, and detects deceleration accompanying release of the accelerator during driving based on changes in accelerator depression amount θ, vehicle speed, clutch engagement, engine rotational speed N, and the like. This deceleration signal is sent to the fuel cut determination section 5.
2, a fuel cut signal is output to the pulse output section 50 at a predetermined engine speed No. or higher, and output of the pulse signal is stopped. In addition, the deceleration signal is input to the depressurization opening determining section 53, and when the engine speed is equal to or higher than a predetermined engine speed No., the engine braking force setting section 54
Determine the vacuum opening degree based on the map shown in Figure 3. That is, when the accelerator is fully opened, the decompression opening is opened according to the maximum engine braking force, and the opening is adjusted so that the engine braking force gradually decreases as the accelerator is depressed, and this opening signal drives the drive unit 55. The output signal is configured to be outputted to the actuator 64 via the output signal. Next, the operation of the two-stroke direct injection engine configured as described above will be described. First, the scavenging air is discharged from the scavenging pump 33 and sent to the intercooler 32.
The supply air cooled by the exhaust gas is always circulated back to the intake side through the bypass passage 35, and scavenging air is introduced into the cylinder 2 side by limiting this return m by the control valve 3G. Here, the opening degree of the control valve 3G is set in inverse proportion to the accelerator depression amount 〇, and when the accelerator depression amount θ is small, more is returned to the opening degree of the control valve 36, and the scavenging air n decreases. The scavenging air is adjusted according to the amount of accelerator depression without causing pump loss. Therefore, when the piston 3 is located near the bottom dead center and the scavenging port 16 is opened together with the exhaust port 11 as shown in FIG. The scavenging air is cooled by the scavenging port 16.
It flows into the inside of the cylinder 2. This scavenging air pushes out residual gas from the exhaust port 11 to perform a scavenging action, and in this way, fresh air consisting only of air is introduced into the cylinder 2 in a short period of time. Then, when the piston 3 rises, the scavenging port 16. When the exhaust port (exhaust port) 11 is closed, the scavenging air ends and the compression stroke begins. Also, exhaust port 1
1 is closed, a predetermined fuel previously stored in the injector IO by a fuel pulse is injected with pressurized air by an air pulse to generate an air-fuel mixture. Then, it is ignited by the spark plug 9 just before top dead center to cause combustion. In this case, the scavenging air flowing in from the scavenging board 16 is injected from the injector IO at the top of the combustion chamber 8 at appropriate timing and time. When the fuel is introduced and guided to the appropriately placed spark plug position, a rich air-fuel mixture is created near the spark plug 9, resulting in stratified combustion. After the explosion caused by this combustion, the piston 3 descends and enters the fat expansion stroke, the exhaust port 11 opens, and exhaust is performed to the extent that it is caused by the cylinder internal pressure.Furthermore, near the bottom dead center, there is an intake stroke accompanied by the scavenging action as described above. This is how the engine is operated. On the other hand, when the engine is operating, the operating condition detection section 46 of the control unit 45. Cylinder air amount calculation unit 47. Fuel injection amount calculation unit 48. The target air-fuel ratio setting unit 49 calculates the fuel injection 2 according to each driving condition except when decelerating while driving.
Based on this, fuel is injected from the injector IO. Therefore, the air-fuel ratio of the in-cylinder mixture is always controlled to the target value. When the accelerator is released to decelerate while driving in such an engine operating state, this is detected by the deceleration detection section 51 and the signal is sent to the fuel cut determination section 52 and the decompression opening determination section 5.
Enter 3. Therefore, if the accelerator depression amount is less than the predetermined accelerator depression amount of 00, the fuel injection amount is immediately stopped and the fuel is cut off as shown in FIG. 4(b) by a cut signal from the fuel cut determination section 52, and the self-destruction becomes impossible. In addition, the decompression opening determining section 5
3 outputs an opening degree signal to the actuator 64, and when the accelerator is fully opened, the pressure reducing valve B1 is opened wide via the link mechanism 63 as shown in Fig. 4 (C). Therefore, the compressed air in the cylinder is It leaks through the pressure reduction passage 60 and acts as a decompressor so that the compression pressure is relatively greatly reduced. Due to this reduction in compression pressure, the internal pressure of the piston leaks whenever the piston is lowered, resulting in an increase in pump work, which results in a large engine braking force as shown in FIG. 4(a). The opening degree of the pressure reducing valve 81 is controlled to gradually decrease in accordance with the amount of accelerator depression, so that the decompression action and the engine braking force smoothly decrease as shown in FIG. 4(a). Then, when the opening signal stops at a predetermined accelerator depression amount θ0, the pressure reducing valve B

[ is fully closed. Furthermore, by stopping the cut signal, the fuel injection amount calculation unit 48 starts injecting the minimum amount of fuel that does not cause a misfire from the injector 10, and the engine returns to self-destruction. In this case, the engine torque change is the fourth The result will be as shown in Figure (a). The engine braking force is variable controlled based on vehicle speed. More fine control can be achieved using parameters such as gears. As described above, according to the present invention, in a system in which engine braking is strengthened by decompression during deceleration in a two-stroke direct injection engine, a large engine brake is effectively applied when the accelerator is fully opened. By variable control of the engine braking force according to the amount of accelerator pedal depression, excessive engine braking is prevented and smooth recovery is possible. Furthermore, since fuel is cut during engine braking due to decompression, it is possible to prevent fuel from blowing out.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the engine braking device for a two-stroke direct injection engine of the present invention, Fig. 2 is a block diagram of the control unit, Fig. 3 is a characteristic diagram of engine braking force, and Fig. 4 (a) is a block diagram of the control unit. ) or C) is a time chart 1 showing the engine braking effect of the amount of accelerator depression. DESCRIPTION OF SYMBOLS 1... Engine main body, 8... Combustion chamber, IO... Injector, 45... Control unit, 51... Deceleration detection part, 52... Fuel cut judgment part, 53... Depressurization Opening degree determining section, 61...Pressure reducing valve, 64...Actuator Patent applicant Fuji Heavy Industries Co., Ltd. Agent Patent attorney Nobu Kobashi Jundo

Claims (1)

[Claims] A two-stroke direct injection engine in which an injector for injecting fuel is installed in the combustion chamber of a two-stroke engine main body, and a pressure reducing valve for decompression is installed on the combustion chamber side, the pressure reducing valve receiving an electrical signal from a control unit. An actuator is provided to open and close the pressure reducing valve, and the fuel is cut from the injector when the accelerator is depressed below a predetermined amount when the vehicle is decelerating while the vehicle is running, and at the same time, the pressure reducing valve is operated to maximize the engine braking force when the accelerator is fully closed. An engine braking device for a two-stroke direct injection engine, characterized in that the engine braking force is controlled to change the opening degree so as to gradually reduce the engine braking force according to the amount of accelerator depression.