JPH07197820A - Miller cycle engine - Google Patents

Abstract

PURPOSE:To provide a miller cycle engine where the structure is simple, the air intake resistance is small, and knocking or generation of NOx is suppressed. CONSTITUTION:In a miller cycle engine provided with a cooling device 22, the phase of an intake valve 8 of the engine provided with intake and exhaust valves 8, 9 relative to the crankshaft is constituted to be driven by an inlet cam shaft 10 which is variable after the bottom dead center of the suction stroke, a non-return valve 13 to open a valve element so that the intake air may flow toward the cylinder 2 is arranged to the inlet system, and the non- return valve 13 is bypassed. The miller cycle engine which is lightweight, simple in the structure, and small in the air intake resistance can be realized without using any rotary valve which is complicated and very heavy as in the conventional miller cycle engine, the charging efficiency of the air to be sucked in the cylinder is improved, and the knocking or generation of NOx is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Miller cycle engine having a high filling efficiency and a remarkable knocking prevention effect.

[0002]

2. Description of the Related Art In the so-called Miller cycle engine, the intake valve closing timing is advanced from the bottom dead center, so that the negative work amount (so-called pumping loss) generated by the intake throttle by the throttle valve at the time of partial load. )
Is substantially reduced to zero to suppress a decrease in cycle efficiency. Further, in order to set the expansion ratio to 11 or more and set the compression ratio to about 10 within the knocking limit, the intake valve closing timing is advanced from the bottom dead center. Also, when supercharged,
The expansion ratio is set to 11 or more, and the intake valve closing timing is advanced according to knocking to reduce the substantial compression ratio, thereby suppressing knocking and maintaining high thermal efficiency. The present inventor has previously proposed, for example, Japanese Patent Publication No.
As shown in Japanese Patent Application Laid-Open No. 8-55329, an improvement 8 plan is proposed in which a normal intake valve having a constant opening / closing timing and a rotary valve capable of changing the closing timing of the intake passage are used together.
Filed as No. 9176.

This is configured such that the intake valve of an engine having intake and exhaust valves is driven by an intake camshaft whose phase can be changed with respect to the crankshaft, and the intake system is operated under full load conditions. A check valve is provided that opens the valve body when the phase of the intake camshaft is changed, without using a complicated and heavy rotary valve.
It is possible to realize a lightweight and simple Miller cycle engine, and to open the check valve valve when the phase of the intake camshaft is changed under full load conditions, so that intake air at full load can be obtained. It has the effect of reducing the resistance to the same level as a normal engine and providing a Miller cycle engine that can exhibit the same output.

In Japanese Patent Application No. 5-189176, the phase of the intake camshaft is changed so as to accelerate the opening / closing timing of the intake valve at the time of partial load or when knocking is suppressed, and the intake valve is closed early to cause a mirror.・ To prevent the cycle from being realized, at this time, the intake valve opens at almost the same time as the exhaust valve, causing exhaust gas to flow back into the intake passage. Prevents backflow of exhaust gas to the passage, and exhaust gas that flows back to the intake passage is sucked into the cylinder in the next intake stroke, resulting in a shortage of oxygen, resulting in incomplete or impossible combustion. To be removed. In addition, Japanese Patent Application No. 5-18917 mentioned above.
In No. 6, by opening the valve body of the check valve,
The resistance of the flow in the intake passage can be reduced to almost the same level as that of the normal engine, and the output can be secured at about the same level.

[0005]

However, in the above-mentioned Japanese Patent Application No. 5-189176, the air once sucked into the cylinder absorbs the heat in the cylinder and is re-exhausted into the intake system. Since it is sucked into the cylinder, the intake air temperature rises, which causes knocking in the Otto cycle engine, and causes a rise in compression temperature, a rise in combustion temperature, and an increase in NOX in the diesel engine. The present invention was devised to solve the above problems, and an object of the present invention is to provide a mirror having a simple structure, low intake resistance, and knocking or NOX generation suppressed. -To provide a cycle engine.

[0006]

According to the Miller cycle engine of the present invention for achieving the above object, the phase of an engine having intake and exhaust valves with respect to the crankshaft of the intake valve is set to the bottom dead center of the intake stroke. A non-return valve that is configured to be driven by an intake cam shaft that can change thereafter and that opens a valve body so that intake air flows toward a cylinder is provided in the intake system, and a cooling device that bypasses the non-return valve. It is characterized in that a bypass passage provided with is provided.

[0007]

[Operation] In the Miller cycle engine of the present invention configured as described above, the phase angle of the intake cam is further advanced when the load is low, and the compression stroke is started by closing the intake valve in the middle of the stroke. While the intake air is warmed in the high temperature cylinder 2, it is discharged before the check valve in the intake port and the intake pipe and further flows into the bypass passage to reduce the substantial stroke volume. ,
The air that has flowed into the bypass passage passes through the cooling device, is cooled, and then flows into the intake pipe. In the next intake stroke, the bypass air cooled as described above merges with the atmosphere, opens the check valve in the intake pipe, and is sucked into the cylinder from the intake port via the intake valve. As a result, the efficiency of filling the air sucked into the cylinder is improved, and knocking or N
Occurrence of OX is suppressed.

[0008]

1 is a mirror cycle engine of the present invention, 2 is a cylinder, 3 is a piston that slides in the cylinder 2, and 4 is a cylinder head. An intake port 6 and an exhaust port 7 are formed in the cylinder head 4 with an ignition plug or a fuel injection valve 5 provided on the center line of the cylinder 2 interposed therebetween, and the openings of both ports 6 and 7 on the cylinder 2 side are opened and closed. An intake valve 8 and an exhaust valve 9 are provided.
The intake valve 8 rotates in synchronism with a crankshaft (not shown) and can change its phase.
It is opened and closed by 1. In addition, 12 is a valve spring. Further, the exhaust valve 9 is opened and closed by an exhaust cam shaft and a lever (neither shown) that rotate in synchronization with a crank shaft (not shown).

A check valve 13 is arranged in an intake pipe 14 attached to the cylinder head 4 in accordance with the intake port 6. The non-return valve 13 has one end fixed to the intake pipe wall 14a by a screw 16 and is supported by a screw 16, and has a valve plate 17 having a through hole 17a and a reed valve 1 made of beryllium copper.
8 and a guide 19 provided outside the reed valve 18, the check valve 13 can be opened by a turning lever 20 attached to the shaft 15 so as to be fitted into the pocket 14b of the intake pipe wall 14a. .

Reference numeral 21 is a bypass passage which is integrally formed with the intake pipe 14 so as to bypass the check valve 13 and, in this example, a cooling device 22 is interposed in the middle thereof. Two
A bypass check valve 3 is fixed to the bypass passage 21 near the cylinder side inlet 21a with a screw 24 and normally closes the inlet 21a. The cooling device 22 does not have to be a dedicated one, and for example, an intercooler in a supercharged engine or the like may be used.

As an apparatus for changing the phase of the intake camshaft 10 that drives the intake valve 8, for example, the opening / closing timing adjusting mechanism 25 shown in FIGS. 4 and 5 can be used. That is, the opening / closing timing adjusting mechanism 25 engraves a helical spline 27 twisted in one direction at the end of the intake camshaft 10 supported by the bearing 26, and coaxially with the intake camshaft 10.
A helical spline 28 twisted in the opposite direction to the helical spline 27 is engraved at an end thereof, and a drive shaft 29 supported by a bearing 26 ′ is provided. Between the splines 27, 28, teeth 30, 31 are formed on the inner surfaces of both ends. Adjusting piece 32 with 3 teeth for each tooth
0 and 31 are set between both shafts so as to mesh with the respective helical splines 27 and 28, and the adjustment piece 32 is operated by an accelerator pedal, a knock sensor (neither is shown), or a predetermined intake pressure or the like (not shown). ), The phase is changed by moving it via the lever 33, and the opening / closing timing of the intake valve 8 is changed. It should be noted that the change of the opening / closing timing of the intake valve is about 1 at maximum as shown in FIG.
80 °. Further, G is a cam drive gear that meshes with a crank gear (not shown).

The operation of the Miller cycle engine of the present invention having the above construction will be described with reference to FIGS. In the Miller cycle engine of the present invention, the expansion ratio is set to, for example, 11 to 16 in the Otto cycle, which is much higher than 8.5 to 10 in the normal Otto cycle engine, and the opening / closing timing of the intake valve at full load is set. As shown in FIGS. 4 and 5, if the opening / closing timing is set to be similar to that of a normal engine, in this case, the expansion ratio and the compression ratio become equal, and knocking occurs due to this high compression ratio. That is, when the intake valve is closed at a point a near the bottom dead center of the intake air, as shown in FIG. 6, the engine inhales over the entire stroke of the intake stroke, and in the compression stroke, from the point a to the point m, the above high expansion. Since the compression ratio is the same as the ratio, the compression pressure and temperature at the point m become excessive and knocking occurs, but this is caught by the knock sensor at the initial stage and an electronic control unit (not shown) uses an actuator (not shown). ), The phase of the intake cam 11 with respect to the crankshaft is advanced by the opening / closing timing adjusting mechanism 25, and the closing timing of the intake valve 8 from the point a to the point b in FIG. Proceed to. Explaining this with the pv diagram of FIG. 6, the piston 3 sucks the volume indicated by A in the entire stroke into the cylinder 2, and once the intake port 6 is opened from the intake valve that is open even after the bottom stroke of the intake stroke. After discharging a volume B of air from the point a to the point b toward the point b, it enters a substantial compression stroke from the point b and compresses to the point n, so both the pressure and the temperature drop, knocking is avoided and stable. It is possible to drive the car. Not only that, but the expansion stroke is longer from the point q to the point r to the point s of the normal engine, which increases the work amount by the area surrounded by the points s-r-a-b. That is, it means that the thermal efficiency is increased.

When the load is low, the phase angle of the intake cam 11 is advanced further, and the intake valve 8 is closed at point c in FIG. 4 to start the compression stroke from point c in FIG. The air of the volume A is discharged again before the check valve 13 in the intake port 6 and the intake pipe 14, which further opens the bypass check valve 23 and flows into the bypass passage 21 to have a substantial stroke volume. It is D.

Although the application of the present invention to the diesel engine is limited to the supercharged engine, the compression stroke is started from the point a in FIG. 6 in the normal engine due to the excessive intake pressure in the intake pipe 14. While the compression pressure becomes the point m and exceeds the maximum allowable pressure of the engine, in the present invention, the opening / closing timing of the intake valve 8 is changed by the opening / closing timing adjusting mechanism 25 shown in FIGS. Since the compression stroke is started from, the compression pressure drops to the point n, and it is possible to maintain the compression pressure below the maximum allowable pressure of the engine.

As described above, when the phase angle of the intake cam 11 is further advanced at the time of low load, the intake valve 8 at the point c in FIG.
Is closed, and the compression stroke starts at point c in FIG. 6, but the air of the volume A sucked into the cylinder 2 becomes
After being warmed in the cylinder 2 at a high temperature, it is discharged again before the check valve 13 in the intake port 6 and the intake pipe 14, which opens the bypass check valve 23 to open the bypass passage 2
1, then flows through the cooling device 22 to be cooled and then flows into the intake pipe 14. In the next intake stroke, the bypass air cooled as described above merges with the atmosphere, opens the reed valve 18 of the check valve 13 in the intake pipe 14, and sucks it into the cylinder 2 from the intake port 6 through the intake valve 8. To be done.

[0016]

The Miller cycle engine of the present invention is
The engine is provided with intake and exhaust valves, and the phase of the intake valve with respect to the crankshaft is configured to be driven by an intake camshaft that can change after the bottom dead center of the intake stroke, and intake air is directed to the cylinder toward the intake system. A check valve that opens the valve body to flow is arranged, and a bypass passage provided with a cooling device is provided to bypass the check valve, so that the opening / closing timing of the normal intake valve is greatly changed. By doing so and by arranging a check valve in the intake system,
Without using a complicated and heavy rotary valve like the conventional Miller cycle engine, it is possible to realize a Miller cycle engine that is lightweight, has a simple structure, and has low intake resistance, and has been sucked into the cylinder once. When the air absorbs the heat in the cylinder and is re-exhausted into the intake system, it is cooled by passing through a bypass passage equipped with a cooling device to improve the efficiency of filling the air taken into the cylinder. In addition, there is an effect of providing a Miller cycle engine in which knocking or NOX generation is suppressed.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a mirror cycle engine of the present invention.

FIG. 2 is a sectional view of an intake valve opening / closing timing adjusting mechanism of the mirror cycle engine of the present invention.

FIG. 3 is a partially enlarged sectional view of FIG.

FIG. 4 is an explanatory view showing changes in valve opening timing with respect to crank angles of intake and exhaust valves of the mirror cycle engine of the present invention.

FIG. 5 is an explanatory view showing changes in valve opening area with respect to crank angles of intake and exhaust valves of the mirror cycle engine of the present invention.

FIG. 6 is a p-v diagram of the Miller cycle engine of the present invention 1; Miller cycle engine 2; Cylinder 3; Piston 4; Cylinder head 5; Spark plug or fuel injection valve 6: Intake port 7; Exhaust port 8: Intake valve 9; Exhaust valve 10; Intake cam shaft 11; Cam 12; Valve spring 13; Check valve 14; Intake pipe 17; Valve plate 18; Reed valve 19; Guide 20; Rotating lever 21; Bypass passage 22 Cooling device 23; bypass check valve 25; intake valve opening / closing timing adjusting mechanism 26, 26 '; bearing 27; helical spline 28; helical spline 29; drive shaft 30; teeth 31; teeth 32; adjusting piece 33; lever.

Claims (2)

[Claims] 1. An intake air system configured to drive an intake camshaft that can change the phase of the intake valve with respect to a crankshaft of an engine having intake and exhaust valves after the bottom dead center of the intake stroke, A mirror cycle engine, comprising: a check valve for opening a valve body so that a flow of water toward a cylinder is provided; and a bypass passage provided with a cooling device for bypassing the check valve. 2. The Miller cycle engine according to claim 1, wherein a bypass check valve that is opened when air once sucked into the cylinder flows backward is disposed in the bypass passage.