JPS61164036A - Intake control device of engine - Google Patents

Abstract

PURPOSE:To improve intake efficiency without damaging stability of combustion in low speed running by delaying in low speed running the opening period of a timing valve interposed in an intake path upstream of an intake valve set to high speed type to delay intake starting period. CONSTITUTION:To a combustion chamber 4 are opened an intake port 6 opened and closed by an intake valve 5 and an exhaust port 8 opened and closed by an exhaust valve 7. And to the intake port 6 is connected an intake path 11 having a carbureter 9 and a rotary valve 10 as a timing valve arranged sequentially from the upstream side. Also, to the rotary valve 10 is connected a valve opening varying unit 12 which is operated by a control unit 13 according to the speed signal from a rotational frequency sensor 14. On the other hand, the intake valve 5 is constituted to be operated with valve lift in which the opening and closing periods are set to high speed type. Thus, in low speed running, the opening period of the rotary valve 10 is delayed to have substantially similar effect to the opening period of delayed intake valve 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an engine intake control device that changes the intake start timing. (Prior Art) Generally, the opening timing of the intake and exhaust valves of an engine is determined by the following steps: It is preferable to change it depending on the operating condition of the engine. For example, during high-speed operation, it is necessary to increase the intake valve opening time to increase charging efficiency in order to obtain high output, but increasing the intake valve opening time is necessary to increase the intake This causes the problem of blowback. Additionally, the overlap period during which both the intake and exhaust valves open has an effect on the amount of residual burnt gas in the intake air, but when the engine is operating at low speed, it is recommended to reduce the amount of residual burnt gas by shortening this overlap period as much as possible. However, shortening the overlap period is preferable to obtain combustion stability.
This shortens the opening time of the intake valve, which leads to insufficient filling during high-speed operation.Also, during high-speed operation, the inertia of the intake flow increases and the filling efficiency increases, so the overlap period must be increased. However, there are no particular negative effects,
Rather, in order to increase the filling amount for the purpose of obtaining high output, the longer the overlap period, the better.

By the way, as described in Japanese Patent Application Laid-Open No. 55-148932, there is no known engine in which a timing valve is provided in the intake vibe of the engine, and an adjustment means is provided to adjust the opening/closing timing of the timing valve according to the load. ing.

(Object of the Invention) The present invention aims to provide an intake control device for an engine that improves intake efficiency and output during high-speed and low-speed operation without impairing combustion stability during low-speed operation. purpose.

(Structure of the Invention) In order to achieve the above object, the present invention provides an intake valve that operates with a valve lift characteristic in which the valve opening timing and valve closing timing are set to a high-speed type, and an intake passage that is opened and closed upstream of the intake valve. Possible with interposed timing valve.

It is characterized by having a control means that delays the opening timing of the timing valve during low-speed operation than during high-speed operation, and by delaying the opening timing of the timing valve during low-speed operation, the intake valve is substantially opened. This has the same effect as delaying the timing.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1 showing the overall configuration of an engine intake control device, I is a cylinder block, 2 is a cylinder head, 3 is a piston, and 4 is a combustion chamber.

An intake port 6 opened and closed by an intake valve 5 and an exhaust port 8 opened and closed by an exhaust valve 7 are opened in the combustion chamber 4, and a carburetor 9 is connected to the intake port 6 from the upstream side. and an intake passage 11 in which a rotary valve 10 as a timing valve is sequentially arranged.

The rotary valve 10 is equipped with a well-known variable valve opening bag [
12, the control unit 13 operates the variable device 12 in response to a rotational speed signal as a speed signal from the rotational speed sensor 14, so that the opening timing can be changed.

As shown in FIGS. 2 and 3, the intake valve 5 has a cam that opens and closes the intake valve 5 so that the valve opening timing and closing timing are set to a high-speed type valve lift characteristic. A cam of the shaft (not shown) is formed. Intake valve 5
Since both the valve opening period and the lift amount are increased, the curve slope of the valve lift characteristic is not as large as that of the normal type (type that satisfies both low speed and high speed), which reduces wear on the cam surface and valve train. There is no disturbance in intake characteristics due to system jumps, etc.

Next, the flow of processing of the control unit 13 will be explained.

First, when the engine is operating at high speed, as shown in Fig. 2, the valve lift characteristics of the intake valve 5 are set such that the valve opening timing and valve closing timing are set to high speed type, and the intake valve 5 is set to a high speed type before top dead center (TDC). The valve opens at approximately 30 degrees, approximately 60 degrees after bottom dead center (BDC).
Since the valve closes at approximately
Compared to the case where the exhaust valve 7 has the same opening time as the conventional exhaust valve 7, the amount of intake air is increased (see the shaded area in FIG. 2), and the output can be improved. Furthermore, the overlap period becomes longer, the filling efficiency increases, and the output can be improved from this point as well.

Note that during high-speed operation, the rotary valve 10 is controlled to have a larger opening area than the intake valve 7.
It has no influence on when to start inhalation.

On the other hand, during low-speed operation, the intake and exhaust valves 5 and 7 open and close in the same way as during high-speed operation, but the control unit 13 controls the valve opening variable device 1 based on a signal from the rotation speed sensor 14.
2, the opening timing of the rotary valve 10 is delayed, the intake start timing is delayed, and the actual overlap period is controlled to be shortened as shown in FIG. 3, so that blowback of intake air is prevented. At the same time, the amount of residual burnt gas is reduced and combustion stability is improved. Moreover, since the actual opening time of the intake valve 5 itself is the same as during high-speed operation, the intake air filling amount is larger than in the conventional case even during low-speed operation (see the shaded area in Figure 3). ), the output can be improved.

(Effects of the Invention) Since the present invention is configured as described above, the timing valve installed in the intake passage upstream of the intake valve so as to be openable and closable allows the timing valve to be opened and closed during high-speed operation without impairing combustion stability during low-speed operation. Not only that, but also during low-speed operation, it is possible to increase charging efficiency and improve output.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an engine intake control device, and FIGS. 2 and 3 show the opening timing of the intake and exhaust valves during high-speed operation and low-speed operation, respectively. FIG. 5...Intake valve, 10...Rotary valve, 12...Valve opening variable device, 13...
...Control unit, 14...Rotation speed sensor. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) In an engine that changes the opening timing of the intake valve, the intake valve operates with a valve lift characteristic in which the opening timing and closing timing are set to high-speed type, and the intake passage upstream of the intake valve can be opened and closed. An intake air control device for an engine, comprising an interposed timing valve and a control means for delaying the opening timing of the timing valve during low-speed operation compared to during high-speed operation, thereby delaying the intake start timing.