JPS61252831A - Intake device of engine - Google Patents

Abstract

PURPOSE:To improve intake efficiency throughout a wide range, according to the method wherein an intake valve is shifted by cams for a low speed and a high speed for opening and closing operation, the length of an intake passage is shifted during low speed running or high speed running, and two shifting operation rotation speeds are differed from each other. CONSTITUTION:A cam 13A for a low speed and a cam 13B for a high speed are disposed in juxtaposition on a cam shaft 10, and during low speed operation, an intake valve 3 is operated by a locker arm 15A brought into contact with the cam 13A for a normally low passed. During high speed running of an engine, a traveling plunger 17 of a locker arm 15B, normally brought into contact with the cam 13B for a high speed and swung, is locked through sliding of a lock member 19, and the plunger presses the end of a screw 26 to directly swing the locker arm 15A for opening and closing operation for a high speed. Meanwhile, an on-off valve 34 is located in an intake passage 32, and the length of an intake line is substantially shortened by opening the on-off valve 34 during a middle speed before operation of the cam 13B for a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine intake system, and more specifically, a low-speed cam and a high-speed cam that close the intake valves at different timings are arranged side by side, and the engine The present invention relates to an intake system for an engine that is provided with a valve opening/closing mechanism that opens and closes the intake valve in conjunction with a low speed cam when the speed is low and a high speed cam when the speed is high based on the rotation speed.

(Prior art) In the intake system of such an engine, a low-speed cam opens and closes the intake valve at low speeds, and a high-speed cam opens and closes the intake valves at high speeds, so the intake valve is not blocked at low speeds. The timing is advanced to prevent intake air blowback, and at high speeds, the intake valve closing timing is delayed to lengthen the intake time, and a single cam allows the intake valve to be the same across the entire range from low to high speeds. Compared to the case where the valve opens and closes at the same timing, it is possible to improve the intake air filling efficiency and the output in both the low speed range and the high speed range. Moreover, since the valve timing is not changed continuously but in stages by switching the cams used, the configuration for changing the valve timing is simpler than, for example, when changing the valve timing continuously. Therefore, it is easy to improve credibility and reduce costs.

Conventional engine intake systems that have these advantages are configured to improve output over the entire range from low speeds to high speeds by simply switching valve timing based on engine speed. (For example, Japanese Utility Model Application Publication No. 57-182205).

However, when using the conventional intake device, the eighth
As shown in the figure, the torque peaks (
d) and (e) are created, resulting in a torque characteristic where there is a torque valley (f) where the torque drops between the low speed range and the high speed range.For example, when accelerating, the acceleration drops by a certain amount during the acceleration. Afterwards, it accelerated again, so I couldn't expect smooth acceleration.

(Problems to be Solved by the Invention) The present invention has been developed in view of the points detailed above. Focusing on the fact that it is possible to improve low-speed torque and high-speed torque by increasing the intake air filling efficiency in the low-speed and high-speed ranges, it is possible to suitably combine switching of valve timing and switching of intake passage length. Although the valve timing is changed in stages, the purpose is to flatten the torque.

(Means for Solving the Problems) The characteristic structure of the engine intake system according to the present invention, which was taken to achieve the above object, is to increase the intake passage length at low speeds and to increase the intake passage length at high speeds based on the engine speed. An intake passage length switching mechanism for shortening the intake passage length is provided, and the engine rotational speed at which the intake passage length switching mechanism switches is different from the engine rotational speed at which the valve opening/closing mechanism switches. The effects and effects thereof are as follows.

(Function) The aim is to improve torque by simultaneously switching the intake passage length, but by making the engine rotation speed at which the intake passage length is changed different from the engine rotation speed at which the valve timing is changed, it is possible to improve torque at low speeds. Opening and closing the intake valve with valve timing, and when operating with a long intake passage length, and opening and closing the intake valve with low-speed valve timing, and
When operating with a short intake passage length, or when operating with a high-speed valve timing to open and close the intake valve, and with a long intake air flow length, and when operating with a high-speed valve timing to open and close the intake valve, and
Torque peaks are formed during operation with a shortened intake passage length.

Therefore, by combining valve timing switching and intake passage length switching, it is possible to improve torque.
Even though the valve timing is changed in stages, the torque peaks are increased compared to when only the valve timing is changed, and the torque troughs in the conventional system are substantially filled in, thereby suppressing the torque drop.

(Effects of the Invention) Therefore, according to the present invention, it is possible to provide an engine intake device that has a simple and inexpensive configuration, can improve torque in the entire range from low speed to high speed, and can flatten the engine.

(Example) Embodiments of the present invention will be described below based on the drawings.

As shown in Figures 2 and 3, the engine has two intake ports (1) and one exhaust port (2) per cylinder.
In other words, it has two intake valves (3) and one exhaust valve (4), and the length of the intake passage (5) is set to 2.
It is equipped with an intake passage length switching mechanism (6) that switches between stages.

The valve train that opens and closes the above-mentioned two types of valves (3) and (4) is configured to open and close each valve (3) and (4), as shown in Figures 4 to 6.
), (4) is moved in the closing direction by a spring (
7) and (8), as well as the cylinder head (
9) One camshaft (10) synchronously driven by a crankshaft (not shown) in the upper widthwise center part
and a valve opening/closing mechanism (1) that opens and closes each valve (3) and (4) as the camshaft (10) rotates.
1) and (12).

The cam shirt L-(10) includes a low-speed cam (13A) and a high-speed cam (13B) that close the intake valve (3) at different timings, and an exhaust cam for opening and closing the exhaust valve (4). (14) are arranged in parallel. The high-speed cam (13B) is formed on each side of the low-speed cam (13A), and both cams (13A),
(13B) is configured such that the profile of the high speed cam (13B) includes the profile of the low speed cam (13^).

Valve opening/closing mechanism (11) for the intake valve (3)
Based on the engine speed, when the speed is low, the intake valve (3) is linked to the low speed cam (13A) to open and close, and when the speed is high, the intake valve (3) is linked to the high speed cam (13B).
) are opened and closed in conjunction with each other, and specifically, the structure is as follows.

In other words, one end is in sliding contact with the low-speed cam (13A) so as to swing with the rotation of the low-speed cam (13A) to open and close the intake valve (3), and the other end is in sliding contact with the intake valve (3). The low-speed rocker arm (15A) that comes into contact with the high-speed rocker arm (15B) that slides on one end of the high-speed cam (13B) so as to swing with the rotation of the high-speed cam (13B) is connected to the rocker shirt. )
(16) so that they can swing independently, and the low-speed rocker arm (15A) is attached to the high-speed rocker so that the low-speed rocker arm (15A) swings following the high-speed rocker arm (15B). Arm (15B)
and the low-speed rocker arm (
15A) is provided with a selector mechanism that can freely switch between an interlock release state and an interlock release state in which the interlock is released so that the cam 15A) swings in response to the low speed cam (13^). To summarize, by switching the selector mechanism to the decoupled state, the low speed rocker arm (15A) is changed to the high speed rocker arm (15B).
The intake valve (3) is opened and closed at the low speed valve timing by swinging the low speed cam (13A) regardless of the
By switching the selector mechanism to the linked state, the low speed rocker arm (15A) is swung by the high speed cam (13B) via the high speed rocker arm (15B), and the intake valve (3) is connected to the high speed valve. It is configured to open and close at the appropriate timing.

The selector mechanism is a high-speed rocker arm (15B)
The high-speed rocker arm (15B) is slidable in the swinging direction against the high-speed rocker arm (15B), and is fixed at the operating position where it protrudes toward the low-speed rocker arm (15A) and comes into contact with the low-speed rocker arm (15A). By pressing the low-speed rocker arm (15A) in the valve-opening direction as the valve swings in the valve-opening direction, the low-speed rocker arm (15A)
) to the high-speed port/7 car arm (15B) to follow and swing, a spring (18) to move and bias this pin (17) to the projecting side, and
) can slide freely along the axis of the rocker shaft (16) only when it slides to the operating position, and by sliding, the circumferential groove (17) formed in the bottle (17)
A lock that changes the position between a lock position where the pin (17) is fixed in the working position by engaging with the groove (17a) and a release position where the pin (17) is released from the circumferential groove (17a) and allows the bottle (17) to slide. A spring (2) is attached to the high-speed rocker arm (15B) to urge the lock play (1-(19)) to the release position.
0) and a hydraulic cylinder (21) that slides the lock plate (19) to the lock position against an urging force. The hydraulic cylinder (21) is an annular cylinder that fits over the rocker shirt (16), and is controlled by a microcontroller based on the engine speed. (25) is an adjustment screw for adjusting valve clearance;
(26) forms the pin contact surface on the low speed rocker arm (15A) side, and the double-ended lock arm (15^),
(15B) is an adjustment screw that adjusts the position of the pin contact surface so that the pin (17) slides into the operating position when it is in sliding contact with the base circle surface of the cams (13A) and (13B) and comes into accurate contact with the pin (17). ,(2
7) is an oil path to the hydraulic cylinder (21);
8) is a spring that biases the low-speed rocker arm (15A) toward the valve.

Valve opening/closing mechanism (12) for the exhaust valve (4)
has an exhaust cam (14) at one end so as to swing as the exhaust cam (14) rotates to open and close the exhaust valve (4).
14) and an exhaust valve (4) at the other end.
Attach the adjustment screw (2) for adjusting the valve clearance.
A rocker arm (30) is supported by a rocker shaft (31).

The intake pipe (32) forming the intake passage (5) portion to the intake port (1) is configured such that its starting end side is bent into a U-shape.

The intake passage length switching mechanism (6) includes the intake pipe (32).
A communication port (33) is formed in the middle of the intake passageway (5) to short-circuit the starting end of the intake passage (5).
) can be opened and closed, and the effective length of the intake passage (5) is lengthened by closing the communication port (33), and the effective length of the intake passage (5) is shortened by opening the communication port (33). A valve (34) is provided. The butterfly valve (34) is operated by an actiator, and as shown in FIG. ) lower engine speed (N2
) is controlled by a computer to open and close. To be more specific, the engine speed (N2) at which the butterfly valve (34) opens and closes, that is, the intake passage length changes, is determined by the intake valve (N2) at the low-speed valve timing.
3) Torque curve (T1) during operation with the intake valve (3) opened and closed and the intake passage length lengthened, and torque curve (T1) when the intake valve (3) is opened and closed at low speed valve timing and the intake passage length is shortened. The intersection point (X) with the torque curve (T2) during operation
, ), and the engine speed (Nl) at which the valve timing is changed is based on the latter torque curve (T2) and the intake valve (3) at the high-speed valve timing.
) is opened and closed, and the engine rotation speed at the intersection (x2) with the torque curve (T3) during operation with the intake passage length shortened.

(35) is a fuel injection valve, and (36) is a head cover.

According to the above configuration, when the speed is low, the intake valve (3) is opened and closed using the low speed valve timing, and when the speed is high, the intake valve (3) is opened and closed using the high speed valve timing, and when the speed is low, the intake passage length is lengthened. However, since this is combined with shortening the intake passage length at low speeds, torque can be improved. Moreover, since the engine speed (N2) at which the intake passage length is changed is not the same as the engine speed (Nl) at which the valve timing is changed, as shown in Figure 1, (1) the intake valve ( 3) When the intake valve (3) is opened and closed and the intake passage length is lengthened; [2] When the intake valve (3) is opened and closed at low-speed valve timing and when the intake passage length is shortened. , [3] Torque peaks (a), (b), (c) when the intake valve (3) is opened and closed at high-speed valve timing and the intake passage is shortened.
) is formed. As a result, compared to switching only the valve timing, the number of torque peaks is increased,
Torque can be flattened.

Note that the present invention may be implemented as follows.

[1] As shown in FIG. 7, the engine speed (N2) at which the intake passage length is changed is set higher than the engine speed (Nl) at which the valve timing is changed. In detail, the engine rotation speed (N1) at which the valve timing is changed is the torque curve (T,) during operation when the intake valve (3) is opened and closed at the low-speed valve timing and the intake passage length is lengthened. High-speed valve timing intake valve (3
) is opened and closed and the intake passage length is lengthened, and the engine rotation speed at the intersection (x3) with the torque curve (Tt') is defined as the engine rotation speed (N) at which the intake passage length is switched.
2), the latter torque curve (Tz") and the torque curve (T,) during operation when the intake valve (3) is opened and closed at high-speed valve timing and the intake passage length is shortened.
The engine rotation speed at the intersection (X4) with If this is the case, the intake valve (3) will be closed at low speed valve timing.
When the intake valve (3) is opened and closed and the intake passage length is lengthened, and when the intake valve (3) is opened and closed with the high-speed valve timing and the intake passage length is lengthened, and when the intake valve (3) is operated with the high-speed valve timing When the intake valve (3) is opened and closed at
), (b'), and (c') are formed, and the torque is flattened.

[2] Instead of short-circuiting the intake passage (5) to shorten the intake passage as in the above-mentioned embodiment, two intake passages (5), a long and a short one, are provided, and these are used alternatively to shorten the intake passage. Switch the aisle length.

[Brief explanation of drawings]

1 to 6 show embodiments of the present invention, FIG. 1 is a torque characteristic diagram, FIG. 2 is a longitudinal sectional front view of the main part, FIG. 3 is a cross-sectional plan view of the main part, and FIG. 4 is a diagram of torque characteristics. Figure 5 is a vertical cross-sectional side view of the main part, Figure 5 is a vertical front view of the main part showing the intake valve open state at low-speed valve timing, and Figure 6 is a longitudinal cross-section of the main part showing the intake valve open state at high-speed valve timing. It is a front view, and the seventh
The figure is a torque characteristic diagram showing another embodiment. FIG. 8 is a torque characteristic diagram of a conventional example. (3)...Intake valve, (13A)...
・Low speed cam, (13B)...High speed cam, (
11)...Valve opening/closing mechanism, (6)...
・Intake passage length switching mechanism.

Claims (1)

[Claims] (1) A low-speed cam and a high-speed cam that close the intake valves at different timings are installed side by side, and based on the engine speed, the intake valve is connected to the low-speed cam at low speeds and the high-speed cam at high speeds. In an engine intake system equipped with a valve opening/closing mechanism that opens and closes in conjunction with the
An intake passage length switching mechanism is provided that lengthens the intake passage length at low speeds and shortens the intake passage length at high speeds based on the engine rotational speed, and this intake passage length switching mechanism switches between the engine rotational speed and the valve opening/closing. An engine intake system in which the mechanism changes at different engine speeds.