JPH04284129A - Intake control device for two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a misfire generated when a temperature of the outside air is increased, in the case of a 2-cycle engine. CONSTITUTION:An engine driven mechanical supercharger 17 is arranged in an engine intake passage to connect intake passages in the upstream and downstream of the mechanical supercharger 17 to each other through a bypass passage 18 and also arranging a bypass control valve 19 in the bypass passage 18 to control an opening of the bypass control valve l9 to a target opening determined by an engine operational condition. An intake air temperature sensor 82 is provided in the engine intake air passage, and when an intake air temperature is increased, the target opening of the bypass control valve 19 is decreased, so that an air amount, supplied into an engine cylinder, is increased to reduce a residual ready combustion gas amount.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air intake control system for a two-stroke internal combustion engine.

0002

[Prior Art] An engine-driven mechanical supercharger is arranged in an engine intake passage, and the intake passage upstream of the mechanical supercharger and the intake passage downstream of the mechanical supercharger are connected to each other via a bypass passage. In addition, a two-stroke internal combustion engine is known in which a bypass control valve is disposed in the bypass passage (Utility Model Application No. 1986-951).
(See Publication No. 37). In such a two-stroke internal combustion engine, a portion of the intake air discharged from the mechanical supercharger is returned through the bypass passage into the intake passage upstream of the mechanical supercharger, thus controlling the opening of the bypass control valve. As the degree increases, the amount of air supplied into the engine cylinder decreases.

Generally speaking, when an engine is started, the engine temperature is low, so the injected fuel is not sufficiently vaporized, making it difficult to achieve good combustion. However, in a two-stroke internal combustion engine, high-temperature burnt gas remains in the engine cylinder, and if the amount of this remaining burnt gas is increased when the engine is started, the heating effect of the remaining burnt gas on the injected fuel will increase, so the injection The fuel is sufficiently vaporized, and thus good combustion can be obtained even when the engine is started. Therefore, in the above-mentioned two-stroke internal combustion engine, when the engine cooling water temperature is low, that is, when starting the engine, the bypass control valve is fully opened to reduce the amount of air supplied to the engine cylinder, thereby reducing the amount of residual burnt gas in the engine cylinder. I am trying to increase it.

0004

[Problem to be Solved by the Invention] However, even when the engine cooling water temperature is low, when the outside temperature rises, the intake air temperature rises, causing the combustion temperature to rise, and thus is discharged into the engine exhaust passage. Exhaust gas temperature increases. When the exhaust gas temperature rises, the pressure in the engine exhaust passage, that is, the exhaust pressure, increases, making it difficult for burnt gas to be discharged into the engine exhaust passage, and thus increasing the amount of burnt gas remaining in the engine cylinder. do. In this way, even when the engine cooling water temperature is low, if the outside temperature is high, the amount of residual burnt gas increases and the amount of air supplied to the engine cylinder decreases considerably, making misfires more likely to occur, resulting in smoke. or a large amount of unburned H
A problem arises in that C and CO are generated. Of course, such problems become more noticeable as the engine temperature increases.

[0005]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, an engine-driven mechanical supercharger is arranged in the engine intake passage, and the intake passage upstream of the mechanical supercharger and the mechanical supercharger are arranged in the engine intake passage. The intake passage downstream of the turbocharger is connected to each other via a bypass passage, and a bypass control valve is disposed within the bypass passage, and the opening degree of the bypass control valve is controlled to a target opening degree determined by the engine operating state. In the two-stroke internal combustion engine, when the intake air temperature or the exhaust gas temperature is detected and the intake air temperature or the exhaust gas temperature becomes higher than a predetermined temperature, the target opening degree of the bypass control valve is reduced. There is.

[0006]

[Operation] When the outside temperature rises and the intake air temperature or exhaust gas temperature becomes high, the target opening degree of the bypass control valve is reduced to increase the amount of air supplied into the engine cylinder.
Reduce the amount of residual burnt gas.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a case where the present invention is applied to a two-stroke diesel engine with a pre-chamber. Referring to Figure 1, 1 is the diesel engine body, 2 is the piston, 3 is the cylinder head, 4 is the main chamber, 5 is the intake valve, 6 is the intake port, 7 is the exhaust valve, 8 is the exhaust port, 9 is the sub Reference numeral 10 indicates a fuel injection valve disposed within the auxiliary chamber 9. Each intake port 6 is connected to a common intercooler 12 via a corresponding branch pipe 11, and the inlet of the intercooler 12 is connected to an air cleaner 14 via an intake duct 13. Disposed within the intake duct 13 are a throttle valve 16 connected to an accelerator pedal 15 and a mechanical supercharger 17 driven by the engine. The opening degree of the throttle valve 16 increases as the amount of depression of the accelerator pedal 15 increases.

A bypass passage 18 branches off from the intake duct 13 between the throttle valve 16 and the mechanical supercharger 17, and this bypass passage 18 is connected to the intake duct 13 downstream of the mechanical supercharger 17. A bypass control valve 19 is arranged within the bypass passage 18 . In the embodiment shown in FIG. 1, the bypass control valve 19 includes a negative pressure chamber 21 isolated from the atmosphere by a diaphragm 20, and a valve body 22 connected to the diaphragm 20 to control the amount of bypass air flowing in the bypass passage 18. do. Negative pressure chamber 2 of bypass control valve 19
1 is a negative pressure conduit 23 and an electromagnetic switching valve 2 that can communicate with the atmosphere.
4 to an engine-driven negative pressure pump 25. On the other hand, the exhaust port 8 is connected to an exhaust manifold 26, and the fuel injection valve 10 is connected to an engine-driven fuel pump 30.

Next, referring to FIG. 2, this fuel pump 30
I will explain about it. Referring to FIG. 2, fuel pump 30
is equipped with a drive shaft 31 driven by an engine, and a fuel supply pump 32 is mounted on this drive shaft 31. Fuel is sucked into this fuel supply pump 32 via a fuel suction passage 33, and fuel discharged from the fuel supply pump 32 is sent into a fuel chamber 35 via a fuel discharge passage 34. Therefore, the inside of the fuel chamber 35 is filled with high pressure fuel. In addition, in FIG. 2, the fuel supply pump 32 is shown rotated by 90 degrees in order to make the structure of the fuel supply pump 32 easier to understand. An externally toothed timing gear 36 is attached to the drive shaft 31, and an electromagnetic pickup 37 is attached facing the outer peripheral surface of the timing gear 36.

A plunger 39 is inserted into the cylinder 38, and a disk-shaped cam plate 41 having a cam surface 40 is fixed to the left end of the plunger 39. Further, the plunger 39 is connected to the drive shaft 31 via a coupling 42. This coupling 42 connects the drive shaft 31 and the plunger 39 so that the drive shaft 31 and the plunger 39 can rotate together and the plunger 39 can move in the axial direction. A roller ring 43 is disposed within the fuel chamber 35 so as to surround the coupling 42, and the roller ring 43 can rotate around the axis of the plunger 39. The roller ring 43 has a lever 44 extending downward.
A cam roller 45 that rolls on a cam surface 40 is mounted on this lever 44.

A timer device 47 having a timer piston 46 is disposed below the roller ring 43, and the lower end of the lever 44 is engaged with the timer piston 46. Note that, in FIG. 2, the timer device 47 is shown rotated by 90 degrees in order to make the structure of the timer device 47 easier to understand. The timer piston 46 includes a high pressure chamber 48 connected to the fuel chamber 35 and a low pressure chamber 49 connected to the fuel suction passage 33 on both sides thereof.
is moved by the pressure difference between these high pressure chambers 48 and low pressure chambers 49. When the timer piston 46 moves, the roller ring 43 is rotated via the lever 44.

On the cam surface 40 of the cam plate 41, the same number of protrusions as the number of cylinders, for example four, are formed.
is constantly pressed onto the cam roller 45 by the return spring 50. When the drive shaft 31 rotates, the plunger 39 is moved in the axial direction when the convex portion of the cam surface 40 engages with the cam roller 45. Therefore, when the drive shaft 31 rotates once, the plunger 39 is reciprocated four times during that period. . A fuel supply passage 52 is intermittently communicated within the pressurizing chamber 51 defined by the plunger 39, and a fuel discharge port 53 communicating with the pressurizing chamber 51 is formed within the plunger 39. On the other hand, four fuel outlets 54 that can communicate with the fuel discharge ports 53 are formed at equal angular intervals around the plunger 39, and each fuel outlet 54 is connected to a corresponding fuel injection valve 10, respectively. Further, the pressurizing chamber 51 is connected to the fuel relief passage 5.
The injection amount control valve 56 is connected to the fuel supply passage 52 through the fuel relief passage 55 .

When the plunger 39 rotates and moves to the left, the fuel supply passage 52 communicates with the pressurizing chamber 51, and thus the fuel in the fuel chamber 35 is fed into the pressurizing chamber 51. At this time, the injection amount control valve 56 is closed. Next, when the plunger 39 rotates and moves to the right, pressurizing the fuel in the pressurizing chamber 51 is started. Next, the fuel discharge port 53
When the pressurized fuel in the pressurized chamber 51 communicates with the fuel outlet 54, the pressurized fuel in the pressurized chamber 51 is sent to the fuel injection valve 10. Next, when the fuel pressure in the pressurizing chamber 51 exceeds the valve opening pressure of the fuel injection valve 10, fuel injection from the fuel injection valve 10 is started. Next, when the injection amount control valve 56 opens, the fuel in the pressurizing chamber 51 flows into the fuel relief passage 5.
5 into the fuel supply passage 52, the fuel pressure in the pressurizing chamber 51 decreases, and thus fuel injection from the fuel injection valve 10 is stopped. Therefore, the injection amount can be controlled by the injection amount control valve 56. On the other hand, when the timer piston 46 moves, the timer ring 4
3 is rotated, the timing of engagement between the protrusion on the cam surface 40 and the cam roller 45 changes. Therefore, it can be seen that the timer device 47 is provided to adjust the injection timing. The injection amount control valve 56 is connected to an electronic control unit 60 as shown in FIG.

Referring to FIG. 1, electronic control unit 60
consists of a digital computer and a bidirectional bus 61.
ROM (read only memory) 62, RAM (random access memory) 63, and CP
It includes a U (microprocessor) 64, an input port 65, and an output port 66. A load sensor 80 that generates an output voltage proportional to the amount of depression of the accelerator pedal 15 is attached to the accelerator pedal 15, and the output voltage of this load sensor 80 is sent to the AD converter 67.
The signal is input to the input port 65 via the input port 65. The electromagnetic pickup 37 generates an output pulse every time the crankshaft rotates by a predetermined angle, and this output pulse is input to the input port 65. The CPU 64 calculates the engine speed from this output pulse. On the other hand, an absolute pressure sensor 81 that generates an output voltage proportional to the absolute pressure in the negative pressure chamber 21 is disposed in the negative pressure conduit 23 of the bypass control valve 19, and the output voltage of this absolute pressure sensor 81 is determined by an AD converter. It is input to the input port 65 via 68. In addition, an intake temperature sensor 8 that generates an output voltage proportional to the intake air temperature is provided in the intake duct 13.
2 is arranged, and the output voltage of this intake temperature sensor 82 is AD
It is input to input port 65 via converter 69 . Further, the output port 66 is connected to the electromagnetic switching valve 24 and the injection amount control valve 56 via corresponding drive circuits 70 and 71, respectively.

A portion of the intake air discharged from the mechanical supercharger 17 is returned through the bypass passage 18 into the intake duct 13 upstream of the mechanical supercharger 17. The amount of returned air increases as the opening degree of the bypass control valve 19 increases, and thus the amount of air supplied into the engine cylinder decreases as the opening degree of the bypass control valve 19 increases. On the other hand, the electromagnetic switching valve 24 is controlled by its duty ratio, and as the duty ratio increases, the time during which the negative pressure chamber 21 is communicated with the negative pressure pump 25 becomes longer than the time during which the negative pressure chamber 21 is communicated with the atmosphere. Become. Therefore, as the duty ratio increases, the negative pressure inside the negative pressure chamber 21 increases,
It can be seen that the opening degree of the bypass control valve 19 increases in this way.

FIG. 3 shows the optimum opening degree of the bypass control valve 19 during normal engine operation, that is, the target opening degree θ of the bypass control valve 19. As can be seen from FIG. 3, the target opening degree θ is a function of the depression amount L of the accelerator pedal 15 and the engine speed N. In FIG. 3, θ0 indicates the target opening θ is zero, that is, the bypass control valve 19 is fully closed, and θ1, θ2, θ3, θ4, θ5
As the temperature increases, the opening degree of the bypass control valve 19 increases. Therefore, the smaller the depression amount L of the accelerator pedal 15 and the lower the engine speed N, the more the bypass control valve 1
The target opening degree θ of No. 9 becomes larger. Furthermore, in a region where the depression amount L of the accelerator pedal 15 is greater than θ=θ0 or in a region where the engine speed N is high, the bypass control valve 19 is maintained in a fully closed state. Note that the target absolute pressure PO in the negative pressure chamber 21 necessary to obtain the target opening degree θ shown in FIG.
The map is stored in advance in the ROM 62 in the form of a map as shown in FIG.

When the outside air is not very high, good combustion can be obtained by maintaining the opening degree of the bypass control valve 19 at the target opening degree θ shown in FIG. However, when the outside temperature rises, the combustion temperature rises, which causes the exhaust gas temperature to rise and the exhaust pressure to rise.As a result, the amount of burnt gas remaining in the engine cylinder increases, making misfires more likely to occur. In order to prevent such misfires from occurring, the target opening degree θ of the bypass control valve 19 is reduced as the outside temperature rises, thereby increasing the amount of air supplied into the engine cylinders and reducing the amount of residual burnt gas. It would be better to reduce the amount. Therefore, in the embodiment according to the present invention, the target absolute pressure PO is multiplied by a correction coefficient K as shown in FIG. This correction coefficient K is set to 1.0 when the intake air temperature THA is lower than THA0;
When it becomes higher than A0, it is increased as the intake air temperature THA becomes higher. Therefore, when the correction coefficient K becomes larger and the target absolute pressure PO becomes higher, the opening degree of the bypass control valve 19 becomes smaller, and as a result, the amount of air supplied into the engine cylinder increases and the amount of residual burnt gas decreases. I am forced to do it. Note that the relationship shown in FIG. 5 is stored in the ROM 62 in advance.

FIG. 6 shows a control routine for the bypass control valve 19, and this routine is executed by interruption at regular intervals. Referring to FIG. 6, first, in step 100, the target absolute pressure PO in the negative pressure chamber 21 is calculated from the relationship shown in FIG. 4 based on the output signal of the load sensor 80 and the engine speed N. Then step 101
Then, the correction coefficient K is calculated from the relationship shown in FIG. 5 based on the output signal of the intake air temperature sensor 82. Then step 10
In step 2, a new target absolute pressure PO is calculated by multiplying the target absolute pressure PO by the correction coefficient K. Next, in step 103, it is determined whether the absolute pressure PM within the negative pressure chamber 21 detected by the pressure sensor 81 is greater than (PO+α). Here, α is a small constant value. PM≧
(PM+α), the process proceeds to step 104 and the duty ratio D of the control pulse supplied to the electromagnetic switching valve 24
T is increased by d, thus causing the absolute pressure PM to decrease. On the other hand, if PM≧(PO+α), the process proceeds to step 105, where it is determined whether PM≦(PO−α), and if PM≦(PO−α), the step
Proceed to step 106. In step 106, the duty ratio D
T is decreased by d, thus causing the absolute pressure PM to increase. In this way, the absolute pressure P inside the negative pressure chamber 21
M is maintained as (PO-α)≦PM≦(PO+α).

FIG. 7 shows another embodiment. In this embodiment, an exhaust temperature sensor 83 is attached to the exhaust manifold 26 instead of the intake temperature sensor. This exhaust temperature sensor 83 generates an output voltage proportional to the exhaust gas temperature, and this output voltage is
It is input to input port 65 via converter 69a. The other points are the same as the embodiment shown in FIG. 1, so the explanation will be omitted. Further, in this embodiment, the correction coefficient K is a function of the exhaust gas temperature THE, as shown in FIG. Further, in order to control the bypass control valve 19, the routine shown in FIG. 6 can be used as is.

[0020]

Effects of the Invention: As the outside temperature rises, the amount of residual burnt gas is reduced, making it possible to prevent misfires from occurring.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a two-stroke internal combustion engine.

FIG. 2 is an enlarged side sectional view of the fuel pump.

FIG. 3 is a diagram showing a target opening degree of a bypass control valve.

FIG. 4 is a diagram showing target absolute pressure.

FIG. 5 is a diagram showing correction coefficients.

FIG. 6 is a flowchart for executing bypass control.

FIG. 7 is an overall view of a two-stroke internal combustion engine showing another embodiment.

FIG. 8 is a diagram showing correction coefficients.

[Explanation of symbols]

13...Intake duct 17...Mechanical supercharger 18...Bypass passage 19...Bypass control valve 82...Intake temperature sensor 83...Exhaust temperature sensor

Claims (1)

[Claims] Claim 1: An engine-driven mechanical supercharger is disposed within an engine intake passage, and an intake passage upstream of the mechanical supercharger and an intake passage downstream of the mechanical supercharger are connected to each other via a bypass passage. At the same time, in a two-stroke internal combustion engine, a bypass control valve is arranged in the bypass passage, and the opening degree of the bypass control valve is controlled to a target opening degree determined by the engine operating state. An intake air control device for a two-stroke internal combustion engine, which reduces a target opening degree of a bypass control valve when an intake air temperature or an exhaust gas temperature becomes higher than a predetermined temperature.