JPH01182525A - Valve timing control device for engine - Google Patents

Abstract

PURPOSE:To improve charging efficiency in a two intake port type four cylinder engine by making the opening timing of both intake valves coincide nearly with each other when engine rotating speed is below fixed value, and their closing timing coincide nearly with each other when the engine rotating speed is above the fixed value. CONSTITUTION:In a four cylinder engine provided with two intake ports 3, 4 and one exhaust port 9 per cylinder, a valve mechanism 44 opens and closes the first and the second intake valve 1, 2 and an exhaust valve 8 on a fixed opening and closing timing, and a tappet valve mechanism 25 is controlled by a control unit 23. In this case, the unit 23 controls the mechanism 25, in a low speed range where the number of engine revolutions is below the fixed value, to close a shut-off valve 22 and to simultaneously make the opening timing of the first and the second intake valve 1, 2 coincide with each other, and on the other hand, in a high speed range where the number of engine revolutions is above the fixed value, to open the shut-off valve 22 and to simultaneously make the closing timing of the first and the second intake valve 1, 2 coincide with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve timing control device for a two-intake, one-bottom, four-cylinder engine. It concerns something that can produce strong resonance effects by changing the timing.

[Prior Art] Multi-cylinder engines that utilize the resonance effect of the intake system to improve charging efficiency are well known.

Here, the resonance effect means that the branched intake passages connected to each cylinder are gathered into one common intake passage on the upstream side, and that a pressure inversion part such as a volume part is provided at a predetermined position of this common intake passage. , the pressure waves (negative pressure waves) generated when the intake valve of each cylinder is opened are propagated back and forth between that cylinder and the pressure inversion section, and the multiple pressure waves thus generated are transferred to the common intake air. By causing resonance within the passage, a composite wave with a large amplitude is generated, and the positive pressure at the peak portion of this composite wave, where the pressure is highest, is made to reach each cylinder just before the intake valve closes. The positive pressure is used to push intake air into the cylinder to increase charging efficiency.

For example, when the opening periods of the intake valves of each cylinder hardly overlap, such as when a six-cylinder engine has three cylinders with non-consecutive firing orders as one cylinder group, the intake port is shown in Figure 11. As shown in the figure, the negative pressure wave generated near the intake port is reversed to a positive pressure wave at the pressure reversal section provided in the upstream part of the intake system, and is returned to the intake port. Since the peak of the pressure of the wave can be made to coincide with the period of the highest pressure of the intake negative pressure as shown by the curve D3, a composite wave having a large amplitude as shown by the curve D3 can be obtained. On the other hand, in an engine in which the opening periods of the intake valves of each cylinder overlap for a considerably long period, such as the ordinary four-cylinder engine shown in Japanese Patent Application Laid-Open No. 62-10466, As shown in Fig. 12, since the inverted wave D4 or the intake negative pressure D5 causes pressure interference between the cylinders, there is a problem that only a composite wave with a small amplitude as shown in the track iD6 can be obtained. However, even if pressure wave supercharging is performed using the resonance effect, the increase in the filling efficiency is extremely small, and there is a problem in that it cannot be practically expected to increase the filling efficiency using the resonance effect.

On the other hand, two-intake one-bottom engines, in which each cylinder has two intake ports, are generally known, and since such two-intake one-bottom engines can secure a sufficient amount of intake air, It is possible to shorten the opening period of the intake valve compared to an intake port type engine. Therefore, in a two-intake port type engine, it is possible to reduce the overlap in the opening period of the intake valves between each cylinder and increase the resonance effect by simply shortening the opening period of the intake valve. However, the resonance effect or intake condition changes in a complex manner depending on the combination of the opening and closing timing of the two intake valves or the engine operating condition, so it is not possible to simply shorten the opening period of the two intake valves. However, there were problems in that the best resonance effect could not be obtained, and other intake conditions could not be sufficiently improved.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and it is possible to obtain a high resonance effect and increase charging efficiency in a two-intake single-bottom four-cylinder engine. It is an object of the present invention to provide a four-cylinder engine capable of improving other intake conditions depending on the operating condition of the engine.

[Structure of the Invention] In order to achieve the above-mentioned object, the present invention provides four intake ports in which each cylinder is provided with a first intake port that is opened and closed by a first intake valve, and a second intake port that is opened and closed by a second intake valve. In a cylinder engine, the second intake valve is opened and closed at a predetermined timing with an opening period of approximately 180 degrees of crank angle, and the first intake valve is opened and closed at a predetermined timing with a valve opening period longer than the second intake valve. An intake valve opening/closing means;
An intake valve opening/closing timing changing means for changing the opening/closing timing of at least one of the first intake valve and the second intake valve, and an engine speed detection means for detecting the rotational speed of the engine are provided, and the engine speed detection means detects the rotational speed of the engine. When the engine rotational speed is below a predetermined value, the opening timing of the first intake valve and the opening timing of the second intake valve are made to substantially match, while the engine rotational speed detected by the engine speed detection means is If the predetermined value is exceeded, intake valve opening/closing timing control means is provided for controlling the intake valve opening/closing timing changing means so that the closing timing of the first intake valve and the closing timing of the second intake valve almost match. An engine valve timing control device is provided.

[Effects of the Invention] According to the present invention, in a four-cylinder engine, since the opening period of the second intake valve of each cylinder is set to approximately 180 degrees of crank angle, the opening period of the second intake valve of each cylinder is The periods have little overlap with each other (4 within a crank angle of 720)
Since two intake valves are opened, the opening period of each intake valve is 72
If 0/4=180° or less, the opening periods of the intake valves do not overlap). Therefore, since it is possible to prevent pressure interference from occurring at the second intake port of each cylinder, it is possible to increase the amplitude of the composite wave of pressure waves generated by the resonance effect. Therefore, if the path length of the intake system between the pressure reversal section and the intake port is set to an appropriate length, the second intake valve of each cylinder will be Pressure peak of composite wave with large amplitude (positive pressure)
is reached.

At low speeds, the opening timing of the first intake valve and the opening timing of the second intake valve are made to coincide with each other by the intake valve opening/closing timing control means. On the other hand, near the top dead center of the intake stroke, the first. Since the opening period of the second intake valve and the opening period of the exhaust valve slightly overlap, when the opening periods of the intake and exhaust valves overlap, the pressure peak of the composite wave caused by the above-mentioned resonance effect occurs. The positive pressure in the combustion chamber strongly scavenges the combustion gas within the cylinder and prevents an excessive rise in temperature within the combustion chamber, thereby improving anti-knocking performance.

On the other hand, at high speeds, the closing timing of the first intake valve and the closing timing of the second intake valve are matched by the intake valve opening/closing timing control means, so that the positive pressure of the pressure peak of the composite wave reaches the cylinder. Immediately after, the first. Since the second intake valve is closed and the positive pressure at the pressure peak is confined within the cylinder, charging efficiency can be effectively increased and engine output at high speeds can be improved.

[Example] Examples of the present invention will be specifically described below.

First Embodiment> As shown in FIG. If you look at it, the first one. When the second intake valve 1.2 is opened, the first . The first intake port 3.4 is connected to the second intake port 3.4. Intake air (air mixture) is drawn into the combustion chamber 7 from the second branch intake passage 5.6, this intake air (air mixture) is compressed by a piston (not shown), and ignited by a spark plug (not shown). The basic configuration is such that a series of steps such as combustion and exhausting the combustion gas to the branch exhaust passage 11 through the exhaust port 9 when the exhaust valve 8 is opened is repeated continuously. Although the explanation is omitted, the second to fourth cylinders #2 to #4 have the same configuration as the first cylinder #1, and the second to fourth cylinders #2 to #4 correspond to the respective members of the first cylinder #1. 4
Each member of cylinders #2 to #4 is given the same number as the first cylinder #l.

The combustion chambers of the first to fourth cylinders #l to #4 are 7°7.7
．． A common intake passage 13 is provided in order to supply intake air to 7, and this common intake passage 13 removes floating dust in the intake air sequentially from the upstream, and at the time of a predetermined low speed, as will be explained later, pressure waves are generated. an air cleaner 14 that acts as a pressure reversal unit; an air flow meter 15 that detects the amount of intake air;
A throttle valve 16 that is opened and closed in conjunction with an accelerator pedal (not shown) is provided. Common intake passage 1 above
The downstream end of No. 3 is connected to a surge tank 17 that cancels out pulsation of intake air and stabilizes the amount of intake air supplied.

The surge tank 17 includes the first to fourth cylinders #1 to 4, respectively.
Independent intake passage 18 for supplying intake air to #4. ...
, 18 are connected, and these independent intake passages 18.
. . , the downstream ends of 1B are respectively ``1. Second branch intake passage 5, 6. ..., connected to 5.6.

Then, as explained later, at a given high speed,
A volume portion 21 is provided that acts as a pressure reversal portion for negative pressure waves generated near the second intake port 4 of the first to fourth cylinders #1 to #4. This volume part 21 is connected to the volume part connection passage 2.
0, the common intake passage 13 at a predetermined position downstream of the air flow meter 15 and upstream of the throttle valve 16.
It is connected to the. The length of the intake system between the second intake port 4 of each cylinder #l to #4 and the volume portion 21 is determined by the length of the second intake valve 2 of each cylinder #l to #4 at a predetermined high speed.
. . , 2 is opened, the second intake port 4.・・・
・The second intake valve 2 is closed at the pressure peak of a negative pressure wave generated in the vicinity of 4, or a composite wave generated by resonance of a positive pressure wave generated when the negative pressure wave is reflected by inverting the pressure in the volume part 21. The length is set so that the second intake port 4 is reached immediately before the second intake port 4 is reached. Further, an on-off valve 22 for opening and closing the volume connection passage 20 is interposed, and the on-off valve 22 is opened at a predetermined high speed in response to a signal from a control unit 23 composed of a microcomputer. It has become. Note that the control unit 23 is a comprehensive control device for the engine CE including intake valve opening/closing timing control means described in the claims of the present application.

By the way, the above 1. The second intake valve 1.2 and the exhaust valve 8 are opened and closed at predetermined timing, and the rotation speed sensor 2
A valve operating mechanism 25 is provided that changes the opening/closing timing of the second intake valve 2 depending on whether the rotational speed of the engine CE detected by the engine speed detection means 4 (engine speed detection means) exceeds a predetermined value. Since this valve operating mechanism 25 is a common one, detailed explanation thereof will be omitted. Note that this valve operating mechanism 25 includes an intake valve opening/closing means and an intake valve opening/closing timing changing means described in the claims of the present application.

Hereinafter, the effects of the above configuration will be explained.

As shown in FIG. 2, in a low speed range as shown in region A where the engine speed is below a predetermined value No, the on-off valve 22 is closed, while the opening timing of the second intake valve 2 is at the third
As shown by curve G3 in the figure, the timing is set to match the opening timing of the first intake valve 1 shown by curve G. At this time, the volume portion 21 is isolated from the common intake passage 13 by the on-off valve 22, so the air cleaner 14 serves as a pressure reversal portion for the resonance effect. As described above, the path length of the intake system between the second intake port 4 of each cylinder #1 to #4 and the pressure reversal section (air cleaner 14) is such that the second intake valve 2 is open when the speed is low. 1st time and when the valve is closed. Since the peak of the composite wave is set to reach the second intake port 3.4, the composite wave due to the resonance effect becomes like curve G4.

In this way, when the opening timing of the second intake valve 2 is made to coincide with the opening timing of the first intake valve l, a negative pressure wave is generated near the second intake port 4, as shown in FIG. Due to the resonance effect caused by the negative pressure wave and the positive pressure wave generated when the pressure is reversed in the air cleaner 14, the first. The intake pressure near the second intake port 3.4 fluctuates like a curve G4. At this time, the exhaust valve 8 is opened until slightly after the top dead center (TDC) of the intake stroke, so near the top dead center of the intake stroke,
The period from when the first intake valve 1 and the second intake valve 2 are opened almost simultaneously until the exhaust valve 8 is closed, The valve period overlaps. Then, during this intake/exhaust overlap period, the first. The intake pressure near the second intake port 3.4 is a fairly high positive pressure due to the resonance effect, so this positive pressure causes the combustion gas remaining in the combustion chamber 7 to be scavenged to the branch exhaust passage 11 side. be done. Therefore, an excessive rise in temperature within the combustion chamber 7 is prevented, and the anti-knocking performance is improved.

On the other hand, as shown in Figure 2, the engine speed is N
While the on-off valve 22 is opened in a high-speed range as shown in region B exceeding o, the closing timing of the second intake valve 2 is
As shown by curve G in the figure, the timing is set to match the closing timing of the first intake valve l shown by curve G. At this time, the on-off valve 22 is opened and the volume part 21 communicates with the common intake passage 13 via the volume part connection passage 20, so the volume part 21 becomes a pressure reversal part of the resonance effect. As described above, the path length of the intake system between the intake port 4 of each cylinder #1 to #4 and the volume part 21 is different when the second intake valve 2 is open and when it is closed at the above-mentioned high speed. Toni No. 1. Since the peak of the composite wave is set to reach the second intake port 3.4, the composite wave due to the intake negative pressure resonance effect becomes like the curve G7.

In this way, when the closing timing of the second intake valve 2 is made to coincide with the closing timing of the first intake valve l, as shown in FIG.
Due to the resonance effect, the first. The intake pressure near the second intake port 3.4 fluctuates like a curve G7. At this time, the first.
Immediately after the pressure peak of the pressure wave due to the resonance effect reaches the second intake port 3.4, the first intake valve 1 and the second intake valve 2 are closed almost simultaneously, so that the positive pressure caused by the pressure wave is applied to the combustion chamber 7. This increases filling efficiency and improves output at high speeds.

Second embodiment> A second embodiment of the present invention will be described below.

As shown in FIG. 5, in the second embodiment, each cylinder #1 to #4
A shatter valve 3° is provided in the first branch intake passage 5 (in FIG. 5, only the first cylinder #1 is shown). An actuator 31 is provided for the shatter valve 30, and the actuator 31 receives a signal from the control unit 23 and operates the shatter valve 30 in the low speed/low load range and medium rotation range, as will be explained later. The shatter valve 30 is closed and opened in other operating ranges. For other configurations, please refer to Part 1! Since it is exactly the same as the embodiment, the explanation will be omitted, but FIG. 1 will be referred to as appropriate.

The on-off valve 21 and the shutter valve 30 in the second embodiment will be described below.
The control method will be explained below.

When the operating state of the engine CE is in a low speed/high load region (average effective pressure Pe>Pe1 and engine speed N≦NO as shown in region I in FIG. 6), the on-off valve 22 is closed and the shatter valve 3o On the other hand, the valve operating mechanism 25 causes the opening timing of the second intake valve 2 to match the opening timing of the first intake valve I, as shown by curve C2, as shown by curve c3 in FIG. The operation in this case is the same as in the first embodiment when the operating state of the engine GE is in the low speed region shown in region A in FIG. 2, so a description thereof will be omitted. .

When the operating state of the engine CE is in a low speed/low load range (Pe≦Pe+N≦NO) as shown in region (■) in FIG. 6, the on-off valve 22 and the shutter valve 30 are closed. At this time, since the first branch intake passage 5 is closed by the Schasta valve 30, intake air is supplied to the combustion chamber 7 only through the second branch intake passage 6. The valve is opened and closed at the timing shown by curve C4 in FIG. Since the peak of the wave reaches the second intake port 4, near the top dead center of the intake stroke, the air in the combustion chamber 7 is scavenged when the intake and exhaust overlap, and the anti-knocking performance is improved.

Further, since the second intake valve 2 is closed before the bottom dead center (BDC) of the intake stroke, blowing back of intake air into the second branch intake passage 6 is prevented, and filling efficiency is improved.

In this case, the effect of reducing the pumping loss due to so-called half-closing of the intake valve occurs, so that the fuel efficiency of the engine CE improves.

When the operating state of the engine CE is in the medium speed range (Nl<N≦N,) as shown by region ■ in Fig. 6, the on-off valve 2
2 is opened and the shirtter valve 30 is closed. At this time,
Since the first branch intake passage 5 is closed by the shatter valve 30, intake air is supplied to the combustion chamber 7 only through the second branch intake passage 6. Then, the second intake valve 2 is opened and closed by the valve operating mechanism 25 at the timing shown by curve C6 in FIG. In this case as well, just like the first embodiment, the peak of the composite wave due to the resonance effect reaches the second intake port 4 when the second intake valve 2 is opened and closed, so that Since the second intake valve 2 is closed immediately after the intake air is forced into the combustion chamber 7 after the point (BDC), the charging efficiency is increased and the output of the engine CE is improved. In this case, the effect of reducing the pumping loss due to the so-called late opening of the intake valve occurs, so that the fuel efficiency of the engine CE is improved.

When the operating state of the engine CE is in the high speed range (N > Nt) as shown in the region ■ in Fig. 6, the on-off valve 2
2 and the shatter valve 30 are opened, while the valve operating mechanism 25 changes the closing timing of the second intake valve 2 from the first intake valve 1 to the first intake valve 1 as shown by a curve C8, as shown by a curve C2 in FIG.
The timing is set to match the valve closing timing. The operation in this case is the same as that in the first embodiment when the operating state of the engine CE is in the high speed region shown in region B in FIG. 2, so a description thereof will be omitted.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of a two-intake, one-bottom, four-cylinder engine showing a first embodiment of the present invention. FIG. 2 is a diagram showing a high speed range and a low speed range in which the on-off valve and the valve train are switched in the engine shown in FIG. 1. FIGS. 3 and 4 show the 1. FIG. 7 is a diagram showing the opening/closing timing of the second intake valve and the characteristics of a composite wave due to a resonance effect with respect to the crank angle. FIG. 5 shows a two-intake bolt type 4 showing a second embodiment of the present invention.
FIG. 2 is a system configuration diagram around a first cylinder of a cylinder engine. FIG. 6 is a diagram showing an operating range in which the on-off valve and the shatter valve of the engine shown in FIG. 5 should be switched. FIG. 7 to FIG. 1θ show the operating conditions corresponding to regions I to I shown in FIG. 6, respectively. It is a figure which shows the opening and closing timing of a 2nd intake valve. FIG. 11 is a diagram showing the characteristics of the intake pressure fluctuation immediately before the intake port due to the resonance effect with respect to the crank angle when there is almost no overlap in the opening periods of the intake valves. FIG. 12 is a diagram showing the characteristics of the intake pressure fluctuation immediately before the intake port due to the resonance effect with respect to the crank angle when there is an overlap in the opening periods of the intake valves. CE...engine, #1 to #4...first to fourth cylinders, 1.2...first. 2nd intake valve, 3.4... 1st.
2nd intake port, 23... control unit (intake valve opening/closing timing control means), 25... valve operating mechanism (intake valve opening/closing means, intake valve opening/closing timing changing means).

Claims (1)

[Claims] (1) In a four-cylinder engine in which each cylinder is provided with a first intake port that is opened and closed by a first intake valve and a second intake port that is opened and closed by a second intake valve, the second intake valve is opened and closed at a predetermined timing. an intake valve opening/closing means which opens and closes the first intake valve at a valve opening period of approximately 180 degrees and opens and closes the first intake valve at a predetermined timing with a valve opening period longer than the second intake valve; and the first intake valve and the first intake valve. intake valve opening/closing timing changing means for changing the opening/closing timing of at least one of the two intake valves, and engine speed detecting means for detecting the rotational speed of the engine; If the value is less than the value, the opening timing of the first intake valve and the opening timing of the second intake valve
While the opening timing of the first intake valve and the closing timing of the second intake valve are made to almost match, if the engine rotational speed detected by the engine speed detection means exceeds a predetermined value, the closing timing of the first intake valve and the closing timing of the second intake valve are made to coincide with each other. 1. A valve timing control device for an engine, comprising an intake valve opening/closing timing control means for controlling an intake valve opening/closing timing changing means so as to substantially coincide with the timing.