JPH0587645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine intake device, and in particular,
The present invention relates to an improvement in an engine intake system that improves output by utilizing inertia supercharging by synchronizing the air column vibration of the intake system with the intake period.

(Prior art) Generally, the flow in the intake pipe is a so-called pulsating flow.
When the intake valve opens and the intake stroke begins, the air column in the intake pipe is accelerated and flows into the cylinder due to the negative pressure generated within the cylinder. During this time, the cylinder internal pressure and volume change with the downward movement of the piston, and at the same time, the intake pipe internal pressure and speed also gradually change both in time and location. The pressure waves generated in the cylinder propagate through the intake pipe, are reflected at the surge tank, and return to the cylinder, and this phenomenon is repeated in the intake system. By synchronizing the frequency of the pressure change caused by the downward movement of the piston with the natural frequency of the intake system, which is determined by the volume of the intake pipe and cylinder, an intake inertia effect can be obtained and the volumetric efficiency can be improved. It is well known that pressure can be achieved.

The natural frequency of the intake system is determined by the length and cross-sectional area of the intake passage, and the average cylinder volume during the intake period.The range of engine speeds that are synchronized with this natural frequency is widened, and the output is achieved by utilizing the intake inertia effect. In order to expand the improvement range, various techniques have been proposed in which the length or area of the intake passage is variable (for example, Japanese Patent Application Laid-Open Nos. 48-58214 and 115819-1989).
No., Japanese Patent Publication No. 119919/1983).

However, since these prior art techniques only vary either the intake passage length or the intake passage area, the effect of expanding the range of output improvement by utilizing the intake inertia effect is small and insufficient. In addition, when considering tuning over a wider range by varying both the length of the intake passage and the area of the intake passage, there is a problem that the engine becomes larger due to the provision of both variable mechanisms. In order to synchronize the passage lengths in the low-speed operating range, there is a problem in that the amount of variation in the length of the intake passage is large, resulting in an increase in the length of the entire intake passage, which impairs compactness.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention provides an engine intake system that effectively changes the intake passage area and intake passage length to improve output, especially in the low-speed operating range, with a compact structure. The purpose is to provide the following.

(Structure of the Invention) The intake device of the present invention has at least a portion of the intake passage leading to one cylinder that is connected to the first intake passage and the second intake passage.
The second intake passage is divided into an intake passage and a switching means for opening and closing the second intake passage to switch the passage area for supplying intake air. while operating, a passage length variable means for varying the length of the first intake passage is provided, and in an operating range where the second intake passage is closed by the operation of the switching means,
The present invention is characterized in that the driving means of the passage length variable means is controlled so that the length of the intake passage becomes shorter in response to an increase in engine speed.

(Effects of the Invention) According to the present invention, the switching means for switching the intake passage area from small in the low rotation range to large in the high rotation range can be realized with a simple structure without increasing the size of the intake passage structure. In addition to expanding the tuning range of the intake inertia effect by switching the intake passage area, the length of the intake passage is shortened in response to the rise in engine speed in the low-speed operating range where the intake passage area is small. By controlling the operation of the drive means of the passage length variable means in this way, the tuning range is further expanded, and the intake inertia effect is achieved over a wider range than when only the intake passage area or length is varied. The output can be improved by

In particular, by changing the intake passage length in the operating range where the intake passage area is small, the amount of displacement of the intake passage length required to tune the natural frequency in response to fluctuations in engine speed becomes smaller, and the intake passage length is reduced. It has various excellent advantages, such as being able to suppress the overall length of the passage as much as possible to ensure compactness, and to synchronize the length of the intake passage to obtain a good output improvement effect.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
1 is a sectional front view of a main part of a multi-cylinder engine equipped with an intake system, and FIG. 2 is a sectional view taken along the line - in FIG. 1.

An intake passage 3 that communicates with the combustion chamber 2 of each cylinder of the engine 1 is provided with a surge tank 5 downstream of the throttle valve 4, and is branched downstream of the surge tank 5 and connected to each cylinder independently.

On the downstream side of the throttle valve 4, the intake passage 3 in the vicinity of the combustion chamber 2 formed in the cylinder head 6 from the outer periphery of the surge tank 5 is connected to a first intake passage 3 having a relatively small passage area by a partition wall 7. Intake passage 3a
and a second intake passage 3b having a relatively large passage area, the first intake passage 3a opens to the first intake port 12a of the combustion chamber 2, and the second intake passage 3b opens to the second intake port 12b. are doing. A switching means 9 having a switching valve 8 is interposed in the middle of the second intake passage 3b, and the switching valve 8 is connected to its rotating shaft 8a.
is linked to the actuator 10 and opens and closes the second intake passage 3b by operation based on a control signal from the control unit 11 of the actuator 10, and supplies intake air only through the first intake passage 3a, and when both intake passages are supplied. The intake passage area is configured to be changed depending on when intake air is supplied through the passages 3a and 3b.

A part of the partition wall 7 downstream of the switching valve 8 is removed so that the first and second intake passages 3a and 3b on both sides communicate with each other, and a fuel injection nozzle 13 is disposed facing this communication part, so that a single A fuel injection nozzle 13 allows fuel to be supplied to both intake passages 3a and 3b.

The surge tank 5 is formed by a casing 14 and a cylindrical rotating member 15 that is rotatably installed inside the casing 14. A passage length variable means 19 for changing the length is configured. This casing 14 is attached to the cylinder head 6 of the engine 1.
An intake manifold is formed which is connected to the cylinder, and independent intake passages 3 corresponding to each cylinder are connected to each other.
Extended portions of the first intake passage 3a and the second intake passage 3b, which are partitioned by a partition wall 7 continuous from the cylinder head 6, are formed along the circumferential direction of the casing 14. Further, the cylindrical rotating member 15 has an internal space that constitutes an expansion chamber downstream of the throttle valve 4, in other words, a substantial surge tank serving as an intake air holding space, and has an opening 15a at the center of one end surface. The opening 15a communicates with the upstream intake passage 3 provided with the throttle valve 4 and serves as an intake inlet, and the cylindrical outer peripheral surface of the rotating member 15 communicates with the inner space and the first and second intake passages on the outer periphery. 3a, 3b
At the same time, each intake passage is made independent for each cylinder by contacting the inner wall surface of the intake passage 3 for adjacent cylinders of the casing 14. A rectangular communication port 15b on the outlet side that communicates with the first and second intake passages 3a and 3b for each cylinder is provided on the circumferential surface of the rotating member 15, and an internal opening 15b is formed in accordance with the rotational position of the rotating member 15. The communication position between the space and the first and second intake passages 3a, 3b is changed, thereby reducing the substantial length of each intake passage 3a, 3b as an independent intake passage from the surge tank 5 to each cylinder. is configured to be variable.

A casing 14 is provided on the other end surface of the rotating member 15.
A shaft portion 15c projecting outward is connected to the casing 14 around the shaft portion 15c and the opening 15a.
A gear 18 fixed to the output shaft of the motor 17 is engaged with an input gear 16 fixed to the end of the shaft portion 15c, and the passage is rotated by rotation of the rotating member 15. A driving means 20 for changing the length is configured. The motor 17 is also driven and controlled by the control signal from the control unit 11.

An engine rotation speed signal from the rotation speed sensor 21 is input to the control unit 11.
The control unit 11 drives and controls the driving means 20 of the switching means 9 for changing the intake passage area and the passage length variable means 19 for changing the length of the intake passage in response to fluctuations in the engine speed, thereby changing the area of the intake passage. The length of the intake passage is adjusted to a value where the air column frequency of the intake passage 3 and the period of the intake period based on the engine speed are synchronized and the intake inertia effect is maximized.

In FIG. 1, 22 is an intake valve, 23 is a cylinder block, and 24 is a piston.

FIG. 3 shows an example of controlling the area of the intake passage by switching the intake passages 3a, 3b according to the engine speed by the control unit 11, and controlling the length of the intake passage by rotating the rotating member 15.

First, the intake passage area is controlled by driving the switching means 9 to open the switching valve 8 when the engine speed reaches the set rotation speed N, and in the low rotation range below the set rotation speed N, the first intake passage 3a Intake air is supplied even with a small intake passage area due to only the first intake passage 3a, while intake air is supplied even with a large intake passage area of the second intake passage 3b in addition to the first intake passage 3a in a high rotation range exceeding the set rotation speed N. This is to switch and control the passage area.

On the other hand, intake passage length control basically increases the passage length when the engine speed is low, and shortens the passage length when the engine speed rises and becomes high. As shown in FIG. 3, the driving means 20 is driven in a low rotation range below the set rotation speed N when the switching valve 8 is closed to shorten the passage length, and when the switching valve 8 opens, the passage length is reduced. is in a shortened state, and is then controlled to a constant length, with the aim of improving output in the low rotation range.

In the above example, since the passage length is varied in addition to the means for changing the passage area, it is possible to make the fluctuation width of the natural frequency of the intake system large and fine, and to obtain the intake inertia effect over a wide range, which increases the output. You can improve your performance.

Additionally, in the low rotation range, combustion performance can be improved by reducing the intake passage area and improving the intake air flow velocity, and in the high rotation range, the intake passage area is large, allowing a large amount of intake air to be supplied satisfactorily. can.

Further, in the above embodiment, the passage length variable means 19 for changing the length of the intake passage is constituted by an intake passage extension formed around the surge tank 5 and a rotating member that rotates along the extension. As a result, the entire structure can be made compact, the structure can be simplified, and reliable operation can be ensured.

In the above embodiment, the passage area of the first intake passage 3a is smaller than the passage area of the second intake passage 3b, but the passage area of both passages is the same or the passage area of the first intake passage 3a is It may be larger than the passage area of the second intake passage 3b.

Regarding changing the passage length, in the above embodiment, the passage lengths of both the first intake passage 3a and the second intake passage 3b are changed.
The length of only the first intake passage 3a may be changed.

Since the above-mentioned inertial supercharging is necessary at high loads, the passage length control as in the embodiment may be performed only at high loads.

Furthermore, in the embodiment described above, a part of the partition wall 7 that partitions the first and second intake passages 3a, 3b is removed so that they communicate with each other, but by eliminating this communication, both the intake passages 3a, 3b may be formed completely independently. At that time, the natural frequency of the intake system changes slightly. Alternatively, a single intake port may be opened in the combustion chamber 2, and the intake passage upstream of this intake port may be divided into a first intake passage and a second intake passage.

On the other hand, the switching means 9 and the driving means 20 for changing the intake passage area and the intake passage length are operated by the control unit 11 which detects the engine rotation speed as in the above embodiment.
It is possible to appropriately adopt means that operates based on a signal that is correlated with the engine speed, such as drive control using an actuator that operates in response to exhaust pressure.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view of main parts of an engine having an intake system according to an embodiment of the present invention, and FIG.
FIG. 3, which is a sectional view taken along the - line in the figure, is an explanatory diagram showing an example of control characteristics. DESCRIPTION OF SYMBOLS 1... Engine, 3... Intake passage, 3a... First intake passage, 3b... Second intake passage, 5... Surge tank, 8... Switching valve, 9... Switching means, 11
... Control unit, 14 ... Casing, 15 ... Rotating member, 19 ... Passage length variable means, 20 ... Drive means.

Claims (1)

[Claims] 1. The intake passage leading to the cylinder is formed at least in part by a first intake passage and a second intake passage, and includes a switching means for opening and closing the second intake passage to switch the passage area for supplying intake air; In the engine intake system, the switching means is operated so that the area of the intake passage increases in response to an increase in the rotational speed, and a passage length variable means for varying the length of the first intake passage. and a drive means for the passage length variable means such that the intake passage length is shortened in response to an increase in engine speed in an operating range in which the second intake passage is closed by the operation of the switching means. An engine intake device characterized in that the operation of the engine is controlled.