JPH018676Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an intake system for an engine that is capable of reducing engine pumping loss and improving thermal efficiency to improve output performance.

Conventionally, engine intake systems have been designed to close the intake valve earlier during light loads than during high loads, so that during light loads with low output,
A system has been proposed in which the amount of intake air is reduced to reduce pumping loss during the compression stroke of the engine, thereby allowing the engine to rotate smoothly. Another type of engine intake system is to install a reed valve in the intake passage upstream of the intake port and downstream of the throttle valve, while bypassing the reed valve and connecting the intake air between the intake port and the reed valve. By opening a bypass passage that supplies pressurized air or pressurized air-fuel mixture to the passage, a reed valve prevents pressurized air from blowing back into the intake passage. This system prevents the supercharger from interfering with the main intake air that passes through the intake passage and is drawn in by negative intake pressure in the high-speed range, ensuring the amount of supercharging in the entire engine speed range. do,
A device with improved filling efficiency and output performance has been proposed (Utility Model Application Publication No. 76436/1983).

However, while the former device can reduce pumping loss during light loads, the intake valve closes early during the intake stroke, which lowers the effective compression ratio during the compression stroke, resulting in lower pressure and temperature at maximum compression. , the disadvantage is that thermal efficiency decreases and output performance decreases. On the other hand, while the latter device has the advantage of high charging efficiency and high output performance in all engine rotation ranges and all load ranges, on the other hand, the pumping loss relative to the output is large at light loads, ensuring smooth engine rotation. The drawback is that it cannot be done.

This idea was made to solve the above-mentioned conventional drawbacks, and the intake valve is designed to open and close the intake port, and to close the intake port earlier when the engine is under light load than when the engine is under high load. an intake valve opening/closing control device that controls opening and closing; a check valve that is provided in an intake passage communicating with the intake port and is opened and closed by a pressure difference between an upstream side and a downstream side, and is closed at light loads and opened at high loads; By providing a supercharger connected to the upstream and downstream sides of the check valve in a bypass passage that bypasses the check valve, and operating at light loads and high loads, pumping loss can be achieved during light loads. In addition, by supplying compressed and high-temperature pressurized air to the engine from the supercharger, the pressure at maximum compression and The purpose of the present invention is to provide a new intake system for an engine that can compensate for a decrease in temperature, improve thermal efficiency, and improve output performance.

Hereinafter, this invention will be explained in detail with reference to the illustrated embodiments.

In FIG. 1, E is a reciprocating engine, 1 is a cylinder, 2 is a piston that reciprocates within cylinder 1, 3 is a combustion chamber defined by cylinder 1 and piston 2, and 4 and 5 are combustion chambers, respectively. An intake port and an exhaust port open at the top of the chamber 3, 6 an intake valve that opens and closes the intake port 4, 7 an intake valve opening/closing control device that controls the timing at which the intake valve 6 opens and closes the intake port 4, and 8 a well-known device. Timing cam (not shown)
This is an exhaust valve that is driven and controlled by the exhaust port 5 and opens and closes the exhaust port 5 at predetermined timing.

Further, 11 is an intake passage that guides intake air from the air cleaner 12 to the intake port 4, 13 and 14 are air flow meters and reed valves as check valves provided in the intake passage 11 sequentially from the upstream side, and 15 is a reed valve 1.
4 is a fuel injection valve facing the downstream intake passage 11, and this fuel injection valve 15 is connected to the air flow meter 13.
The air-fuel ratio of the air-fuel mixture is controlled by the output of a microcomputer 16 which performs arithmetic processing upon receiving a signal representing the amount of intake air from the air-fuel mixture.

18 is an intake passage 11 upstream of the reed valve 14.
19 is a bypass passage 18 which branches off from the reed valve 14 and joins the intake passage 11 downstream of the reed valve 14.
A supercharger 21 is installed in the supercharger 1 and is driven by the engine 1 or exhaust gas to pressurize and supercharge air downstream of the reed valve 14.
A return passage 9 communicates the upstream side and the downstream side, and 22 is a relief valve provided in the return passage to regulate the maximum boost pressure.

On the other hand, the intake valve opening/closing control device 7 has a structure as shown in FIGS. 2 and 3. That is, the rotating shaft 27 of the pulley 26 is rotatably supported on one side 25a of the cam storage case 25 via a bearing 28. The pulley 26 is synchronized with the crankshaft (not shown) of the engine E by a timing belt 29 wound around the pulley 26, and is configured to rotate (1/2) per rotation of the crankshaft of the engine E.

The inner end of the rotating shaft 27 of the pulley 26 is formed into a spline shaft 31. The spline shaft 3
1, one end of the rotating shaft 33 with the timing cam 32 fixed approximately in the center is fitted so as to be slidable in the axial direction, while the other end of the rotating shaft 33 is fitted to the other side of the cam storage case 25. 25b through a bushing 35 so as to be rotatable and movable in the axial direction, and the other end of the rotary shaft 33 is fitted into the blind hole 34 by a spring 36 to the left side in FIG. It is biased towards. A pair of collars 37 and 38 are fixed to the outer periphery of one end of the rotating shaft 33, and an annular groove 39 between the collars 37 and 38 is fixed to the outer periphery of one end of the rotating shaft 33.
A roller 42 rotatably attached to the tip of a substantially L-shaped rod 41 is inserted into the roller. Rod 4 above
1 is slidably fitted into one side 25a of the cam storage case 25, and is adapted to be interlocked with an accelerator pedal (not shown). Therefore, when the accelerator pedal is depressed and the load is high, the rod 4
1 is displaced in the direction of arrow
It is designed to be displaced to the right in the figure. In addition,
When the roller 42 is in contact with the collar 37 or 38, it rotates together with the collar 37 or 38 to prevent the rotating shaft 33 and the rod 41 from interfering with each other.

On the outer periphery of the timing cam 32, a low speed cam surface 45 and a high speed cam surface 46 are formed continuously in the axial direction. As shown in FIG.
The peak portion 45a is located at the high-speed cam surface 46 with respect to the rotational direction of the timing cam 32 shown by the arrow Y in FIG.
has a falling phase earlier than the peak portion 46a of
Moreover, the ridge portion 45a has a steeper slope than the ridge portion 46a.

The above-mentioned low speed cam surface 45 or high speed cam surface 46
In this case, the spring force of a spring 52 that presses a spring seat 51 fixed to the end of the valve shaft 6a of the intake valve 6 is used to urge the valve shaft end 6b of the intake valve 6 into constant contact with the spring seat 51.

Therefore, the opening/closing timing of the intake valve 6 is controlled by the low-speed cam surface 45 and the high-speed cam surface 46 of the timing cam 32, and when the engine E is under a light load, the valve shaft of the intake valve 6 is As shown in FIG. 2, the end 6b is in contact with the low-speed cam surface 45, so the valve lift of the intake valve 6 is
As shown by curve L in Fig. 4, it falls quickly.On the other hand, when engine E is under high load,
The rotating shaft 33 and the timing cam 32 are connected to the rod 4.
1. The valve shaft end 6b of the intake valve 6 is displaced by the roller 42 in the direction shown by the arrow P in FIG. It becomes as shown in the middle curve H. Therefore, the closing timing of the intake valve 6 is earlier under light loads than under high loads.

In addition, in FIG. 4, TDC is the top dead center of the piston during the intake stroke, and BDC is the bottom dead center of the piston during the intake stroke.

In the engine intake control device having the above configuration,
Now, assuming that the engine E is operating under a light load, the closing timing of the intake valve 6 is as shown by the curve L in FIG. 4, and when the load is high (as shown by the curve H).
Since the engine speed is faster than that of the engine E, the amount of intake air is small, and therefore the power required for the compression stroke, that is, the pumping loss, is reduced, and the engine E can rotate smoothly.

Also, at this time, the air-fuel mixture in the combustion chamber 3 of the engine E tries to lower the pressure and temperature at maximum compression due to a decrease in the effective compression ratio because the closing timing of the intake valve 6 is early. At a certain light load, the intake negative pressure is small, the reed valve 14 is closed, and only the supercharged air (indicated by hatching M in Fig. 4), which has been compressed by the supercharger 19 and has reached a high temperature, enters the combustion chamber 3. is supplied, it is possible to compensate for the decrease in pressure and temperature, improve thermal efficiency, and improve output performance. Furthermore, in this operating state, the reed valve 14 is closed by the boost pressure, thereby preventing intake air from blowing back.

Furthermore, when the load is light, the thermal efficiency improves, so if the same output as before is obtained, the microcomputer 16 reduces the fuel injection amount of the fuel injection valve 15 by the amount of the improved thermal efficiency, thereby reducing fuel consumption. Can be made smaller.

On the other hand, if the engine 1 is operating under high load, the valve lift of the intake valve 6 will be the curve H in Fig. 4.
As shown in the figure, the intake valve 6 opens before the top dead center and closes at a certain timing after the bottom dead center. Therefore, main intake air is supplied to the intake port 4 of the engine E through the intake passage 11 and reed valve 14 due to intake negative pressure, and pressurized air is supplied by the supercharger 19 through the bypass passage 18. This results in improved filling efficiency and improved output performance. In addition, the cross-hatched part N in Figure 4
is the supercharging amount at the beginning of the compression stroke.

Note that the intake valve opening/closing control device is not limited to the one in the above embodiment, but may be of any structure as long as it closes the intake valve earlier during light loads than during high loads. It's okay.

As is clear from the above explanation, the engine intake control device of this invention uses the intake valve opening/closing control device to close the intake valve earlier at light loads than at high loads. It is possible to reduce pumping loss and allow the engine to run smoothly.In addition, a check valve is installed in the intake passage that closes at light loads and opens at high loads, and a bypass passage that bypasses the check valve is installed. A supercharger that operates at light loads and high loads is installed, and the supercharger supplies only high-temperature pressurized air to the engine during light loads, reducing the pressure and temperature at maximum compression caused by the pumping loss countermeasures mentioned above. It compensates for the decrease, improves thermal efficiency, and improves output performance.Furthermore, since the amount of intake air is small under light loads, fuel efficiency can be improved.

Further, in the engine intake system of this invention, since the opening/closing timing of the intake valve is variably controlled by the intake valve opening/closing control device, the conventional throttle valve can be omitted.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of an embodiment of this invention, Fig. 2 is a sectional view of the intake valve opening/closing control device, Fig. 3 is a sectional view taken along line A-A in Fig. 2, and Fig. 4 is a sectional view of the intake valve. FIG. 3 is a characteristic diagram showing valve lift. 4...Intake port, 6...Intake valve, 7...Intake valve opening/closing control device, 11...Intake passage, 14...Reed valve, 18...Bypass passage, 19...Supercharger.

Claims (1)

[Scope of utility model registration request] An intake valve that opens and closes the intake port, and an intake valve opening/closing control device that controls the opening and closing of the intake valve so that the closing timing of the intake port is earlier when the engine is under a light load than when the engine is under a high load, and an intake valve opening/closing control device that communicates with the intake port. A check valve is provided in the intake passage and opens and closes depending on the pressure difference between the upstream and downstream sides, and closes when the load is light and opens when the load is high. An intake system for an engine, comprising a supercharger that is provided in a bypass passage that bypasses a stop valve and operates during light loads and high loads.