JPH0521631Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a supercharger rotation control device for a two-stroke internal combustion engine equipped with a supercharger functioning as a scavenging pump.

[Conventional technology and problems]

With a two-stroke internal combustion engine, there is less pumping loss due to the piston during deceleration. Therefore, engine braking performance is not sufficient compared to a four-stroke internal combustion engine. As a measure to improve engine braking performance, for two-stroke internal combustion engines that have a mechanical supercharger as a scavenging pump, the air passing through the supercharger during deceleration is removed from the negative pressure downstream of the throttle valve. Since the pressure is increased to positive pressure or atmospheric pressure downstream of the supercharger, engine braking performance can be improved by the amount of work done. However, if this continues for a long time, the temperature of the intake air downstream of the supercharger becomes excessive, which is not desirable from the viewpoint of engine durability.

The purpose of this invention is to achieve a balance between engine braking performance and engine durability in a two-stroke internal combustion engine equipped with a supercharger.

[Means for solving problems]

According to this idea, two systems equipped with a supercharger in the intake system
In a cycle internal combustion engine, a bypass passage bypassing a supercharger, an on-off valve installed in the bypass passage, a deceleration state detection means, an intake air temperature detection means downstream of the supercharger, and a deceleration state detection means downstream of the supercharger. A supercharger control device for a two-stroke internal combustion engine is provided, which comprises a control means for opening an on-off valve when intake air temperature is high.

〔Example〕

FIG. 1 shows the general structure of a six-cylinder two-stroke internal combustion engine having an intake valve and an exhaust valve to which this invention is applied, and FIG. 2 shows one cylinder. As will be explained later, this type of two-stroke internal combustion engine generates an exhaust swirl during the backflow of exhaust gas after blowdown, creating a stratification effect in which fresh air is concentrated near the spark plug at the top of the combustion chamber. This was devised to improve ignitability during operation. However, this invention is not limited to this type of two-stroke internal combustion engine, but can also be applied to ordinary piston-valve type two-stroke internal combustion engines. 1 and 2, 10 is the main body of the internal combustion engine, which includes a cylinder block 12, a cylinder bore 14, a crankshaft 15, and a piston 1.
6, a combustion chamber 17, a cylinder head 18, and a spark plug 19. The cylinder head 18 has two intake ports 20a, 20b and two exhaust ports 22a, 22b, and intake valves 24a, 24b for opening and closing the respective intake ports and exhaust ports.
It is a so-called four-valve type equipped with exhaust valves 26a and 26b. The intake valve and exhaust valve each have their own cam 2.
It is driven to open and close by 7 and 28. 30 and 31 are valve springs. Exhaust port 22a, 2
2b is selected in such a shape that a swirl of the exhaust gas is obtained in the cylinder bore about its vertical axis when the exhaust gas flows back into the cylinder bore due to its negative pressure after blowdown.

In FIG. 1, 32 indicates a surge tank.
It is connected to the number of intake pipes 33 that corresponds to the number of cylinders.
The intake pipe 33 has an internal partition wall 33-1, and two intake passages 34a and 34b are formed therein and connected to the intake ports 20a and 20b, respectively. The second intake passage 34b has an effective dimension equal to that of the first intake passage 34b.
a, and an intake control valve 36 is installed. The intake control valve 36 of each cylinder is connected to a link means 36'.
is connected to the actuator 37 by. The actuator 37 is, for example, a diaphragm mechanism operated under negative pressure, and is switched between negative pressure and atmospheric pressure by a switching valve (not shown).
can selectively take a position where the intake passage 34b is opened or a position where it is closed. Intake control valve 3
6 is closed when the load is light and opened when the load is high, as will be described later. Fuel injector 38a, 38b
are arranged in the intake passages 34a, 34b. 40
Reed valves a and 40b are installed as necessary to control backflow.

An intercooler 42, a mechanical supercharger 44, a throttle valve 46, an air flow meter 48, and an air cleaner 50 are arranged in this order in the intake system upstream of the surge tank 32. The mechanical supercharger 44 is constituted by, for example, a roots pump or a vane pump, and a pulley 44-2 is provided on the drive shaft 44-1, and a belt 44-3 drives the crankshaft 15.
It is connected to the upper pulley 15'. Mechanical supercharger 4
A bypass control valve 45 is installed in a bypass passage 44' that bypasses the intake pipe 4, and serves to adjust the intake pipe pressure. The bypass control valve 45 is configured as an electromagnetic on-off valve in this embodiment. In this embodiment, the intercooler 42 is configured as an air-cooled type, and includes an inlet container 42-1, an outlet container 42-2,
It is composed of a heat exchange tube 42-3 communicating therebetween, and a fin 42-4 attached on the heat exchange tube 42-3.

The exhaust manifold 54 is #1 in this example.
Two separate cylinder groups are installed for cylinder groups up to #3 and cylinder groups #4 through #6, respectively. This grouping is such that ignition alternates between these two groups. That is, in this embodiment, the firing order is #1, #6,
Assume that the order is #2, #4, #3, and #5. By grouping the engines with alternating ignition, the exhaust pressure of one cylinder during the scavenging stroke is not affected by the exhaust pressure of other cylinders. The exhaust manifolds 54 of the cylinder groups #1 to #3 and the cylinder groups #4 to #6 are each connected to a dedicated catalytic converter 56 (which may also be used as a muffler or a dedicated muffler may be installed separately).

A distributor 58 is connected to the spark plug 19 of each cylinder, as is well known, and is controlled by an igniter and an ignition coil (not shown) so that ignition is performed at a desired crank angle.

The control circuit 60 includes injectors 38a and 38b.
, ignition control, and further controls the intake control valve drive actuator 37, and can be configured as, for example, a microcomputer system. The control circuit includes an air flow meter 48 that detects the intake air amount Q, a crank angle sensor 62 (pulse signal every 360° CA) that generates a pulse signal for each rotation angle of the crankshaft, and a crank angle sensor 64 (pulse signal every 30° CA). signal),
The actuator is connected to operating condition sensors such as the above, and controls the actuator described above. Since this control is not directly related to this invention, detailed explanation will be omitted.

65 is a bypass passage 45 according to this invention.
A bypass control valve drive circuit that drives the bypass control valve 45 above is shown. Although the bypass control valve drive circuit 65 can be made to coexist with the control circuit 60, it is constructed as an independent circuit for convenience of explanation.
That is, the drive circuit 65 has a comparison circuit 65-1, one input of which is connected to a temperature sensor 66 provided in the intake pipe downstream of the supercharger 44. The temperature sensor 66 generates a voltage according to the temperature T of the air from the supercharger 44. The other input of the comparison circuit 65-1 is set to a voltage corresponding to the upper limit T _MAX of the temperature of the intake air downstream of the supercharger 44. The output of comparator 65-1 is connected to one input of AND gate 65-2, and the other input of AND gate 65-2 is connected to idle switch 68. The idle switch 68 is a switch that is turned on when the throttle valve 46 is in the idle position and turned off when the throttle valve 46 is released from the idle position. AND gate 65
-2 output is connected to transistor 65-3,
This transistor 65-3 controls the drive of the excitation coil 45A of the solenoid valve 45.

FIG. 3 shows the intake valve 24a in one cylinder determined by the profile and orientation of the cams 27 and 28.
24b and the operation timings of the exhaust valves 26a and 26b. First, the exhaust valves 26a, 26
b begins to open at 80° before bottom dead center (BDC) and finishes closing at 40° after bottom dead center (BDC). On the other hand, the intake valve 24
a and 24b begin to open at 60° before bottom dead center (BDC),
Closes at 60° after bottom dead center (BDC). I indicates the fuel injection period, starting from 20° after bottom dead center (BDC),
It ends just before the intake valve closes.

Next, the combustion operation of a two-stroke internal combustion engine equipped with an intake valve and an exhaust valve to which this invention is applied will be explained. When the engine is under light load, the intake control valve 36 is closed and the intake air is passed through the first intake passage 34.
It is introduced into the institution only through a. piston 1
6. In the process of descending, first the bottom dead center (BDC)
The exhaust valves 26a and 26b begin to open at around 80 degrees forward.
Therefore, the exhaust gas from the combustion chamber flows out to the exhaust ports 22a, 22b as indicated by arrow P in FIG. 4A, and so-called blowdown occurs, but this blowdown is weak and ends quickly. When the piston 16 further descends, the inside of the cylinder bore 14 becomes weakly negative, so the exhaust ports 22a, 22b
Due to the pressure difference between the two cylinders, the exhaust gas flows back toward the cylinder bore as shown by arrow Q (Fig. 4B). Because of the shapes of the exhaust ports 26a and 26b, a swirl of exhaust gas as shown by arrow R is formed within the cylinder bore. Around this time, intake valve 24
a (also 24b) begins to open, but its lift is still small, the throttle valve 46 is throttled, the intake control valve 36 is closed, the intake passage 34b with a large effective dimension is closed, and the Since air can flow only through the intake passage 34a, substantially no fresh air is introduced. When the piston 16 further descends, the swirl of exhaust gas continues, and on the other hand, the lift of the intake valves 24a and 24b increases, so fresh air is introduced into the cylinder bore as shown by arrow S. At this time, the exhaust gas rides on the swirl and flows into the cylinder bore. On the other hand, stratification is achieved in which the fresh air mixed with the injected fuel gathers in the vicinity of the spark plug electrode above the swirled exhaust gas portion (FIG. 4C). This stratified state of the exhaust gas R and fresh air S is maintained even when the piston reaches the bottom dead center (BDC) (FIG. 4D).
In E, the intake valves 24a and 24b are closed to prevent fresh air from blowing back. The piston then moves upward, but this stratified state is maintained until compression is completed, making it easy to ignite the fresh air near the spark plug.

In high engine load conditions, the intake control valve 36 is opened. Therefore, the intake passage 34b, which has been closed until now, is opened. In FIG. 5, when the exhaust valves 26a and 26b open during the downward movement of the piston 16, the exhaust gas in the cylinder bore 14 is discharged to the exhaust ports 22a and 22b by a blowdown P, but the blowdown is performed under a light load. It is stronger and lasts longer than usual (Figure 5a), and a large amount of exhaust gas is discharged to the exhaust port. The intake valves 24a and 24b begin to open at the time shown in FIG.
It is done like this. At this time, the intake port 20a,
Fresh air is introduced from both ports 20b, and this fresh air flows from top to bottom along the cylinder bore wall as shown by arrow T, causing the exhaust gas to flow out to exhaust ports 22a and 22b as shown by arrow U. Scavenging is achieved. At the time point (c) in FIG. 5, a negative pressure component appears in the pressure wave pulse due to the strong blowdown, and the exhaust ports 22a and 22b temporarily become negative pressure, which further promotes the introduction of fresh air T into the cylinder bore. A part of the fresh air flows out to the exhaust ports 22a and 22b like V and is stored. When the pressure in the exhaust ports 22a, 22b returns to positive pressure, this stored fresh air flows back into the cylinder bore as shown by arrow W, generating a swirl X of fresh air (FIG. 5D). This causes turbulence and improves flame propagation after ignition. At the time point E in FIG. 5, the intake valves 24a and 24b have completed closing, and fresh air is prevented from blowing back.

In the operation of a two-stroke internal combustion engine to which this invention described above is applied, the supercharger 44 serves to improve engine braking performance during deceleration operation. The reason is that the throttle valve 46 is fully closed during deceleration, and a strong negative pressure is created downstream of the throttle valve 46. on the other hand,
The downstream side of the supercharger 44 is at positive pressure, or at least atmospheric pressure, due to the high speed rotation of the supercharger 44. Therefore, a load is applied to the supercharger 44, which acts as an engine brake. However, if this state continues, there is a risk that the air temperature downstream of the supercharger will increase. That is, the temperatures at the inlet and outlet sides of the supercharger are T ₁ and T ₂ , and the pressures are P ₁ and P ₂ , respectively.
Then, there is a relationship of (P ₂ /P ₁ ) ^K = (T ₂ /T ₁ ) ^K-1 , and when the value of P ₂ /P ₁ is large, the temperature T ₂ on the outlet side also becomes high.

According to this invention, the idle switch 68 generates a signal of "1" in the deceleration state. On the other hand, the comparator 65-1 generates an output of "0" when the intake air temperature T detected by the temperature sensor 66 has not reached the maximum value _TMAX , and the AND gate 65-1 outputs "0".
produces an output of "0". Therefore, a signal of "0" is output to the transistor 65-3. Therefore, the transistor 65-3 is turned OFF, the solenoid 45A of the solenoid valve 45 is demagnetized, and the solenoid valve 45 is demagnetized.
will be closed. At this time, since there is negative pressure between the throttle valve 46 and the supercharger 44 and positive pressure or at least atmospheric pressure downstream of the supercharger 44, a large driving loss occurs in the supercharger, which acts as an engine brake. It turns out.

In the deceleration state, the comparator 65-1 detects that the intake air temperature T detected by the temperature sensor 66 is the maximum value _TMAX.
When it becomes larger, an output of "1" is generated, and the idle switch 68 generates a signal of "1" when the throttle valve 46 is in the idle position. Therefore,
AND gate 65-2 outputs a signal of "1" to transistor 65-3. Therefore, the transistor 65-3 is turned on, energizing the solenoid 45A of the solenoid valve 45, and the solenoid valve 45, which is normally closed, is opened. As a result, the bypass passage 44' is opened and some air bypasses the supercharger 44. Then, since there is a negative pressure between the throttle valve 46 and the supercharger 44 and a positive pressure downstream of the supercharger 44, the air flows from the supercharger 44 toward the intake pipe side via the bypass passage 44' as shown by the arrow x. A flow is formed,
The air will circulate through the supercharger 44 and the bypass passage 44'. As a result, high-temperature air no longer enters the cylinder bore, and the durability of the engine is no longer adversely affected.

During operation other than deceleration, the AND gate outputs a "0" signal, so the solenoid valve 45 is kept closed.

The operation of the electromagnetic valve 45 described above is realized by the theoretical circuit 65 in the embodiment, but it can also be extremely easily configured by software of a microcomputer. FIG. 6 shows the flowchart. Since the flowchart is extremely simple, its explanation will be omitted.

[Effect of idea]

According to this invention, the valve device 45 on the passage 44' that bypasses the supercharger is closed during deceleration, the temperature factor is detected, and the valve device 45 is opened when the intake air temperature is higher than a predetermined value, thereby applying engine braking. It is possible to achieve both performance and engine protection.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the entire system according to an embodiment of this invention. Figure 2 is a diagram showing the cross section of one cylinder (first
(view along the - line in the figure). FIG. 3 is an angle diagram of the operation timing of the intake valve and exhaust valve of one cylinder during one cycle of the engine. FIG. 4 is a diagram illustrating combustion operation in one cycle of a two-stroke internal combustion engine with an intake valve and an exhaust valve according to an embodiment of the present invention under light load. FIG. 5 is a diagram illustrating combustion operation in one cycle of a two-stroke internal combustion engine with an intake valve and an exhaust valve according to an embodiment of the present invention under high load. 6th
The figure is a flowchart of the operation of the solenoid valve for bypass control. 10...Engine body, 17...Combustion chamber, 24a,
24b...Intake valve, 26a, 26b...Exhaust valve,
34a, 34b...Intake passage, 36...Intake control valve, 38a, 38b...Fuel injector, 42
...Intercooler, 44 ...Mechanical supercharger, 4
4'... Bypass passage, 45... Solenoid valve, 54...
...Control circuit, 65...Solenoid valve drive circuit, 66...
Temperature sensor, 68...throttle switch.

Claims (1)

[Scope of utility model registration request] In a two-stroke internal combustion engine equipped with a supercharger in the intake system, a bypass passage bypassing the supercharger, an on-off valve installed in the bypass passage, a deceleration state detection means, and an intake air temperature detection means downstream of the supercharger. A supercharger control device for a two-stroke internal combustion engine, comprising: a control means for opening an on-off valve during deceleration and when intake air temperature downstream of the supercharger is high.