JPH0578648B2 - - 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 by the negative pressure generated within the cylinder and flows into the cylinder. During this time, the pressure and volume inside the cylinder change with the downward movement of the piston, and at the same time the pressure and speed inside the intake pipe 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 intake pipe and cylinder volume, an intake inertia effect can be obtained and the volumetric efficiency can be improved. It is well known that output 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 intake passage length or intake passage area is varied (for example, Japanese Patent Application Laid-Open No. 48-58214, Japanese Patent Application Laid-Open No. 56-115819).
No., Japanese Patent Publication No. 58-119919).

However, these prior art techniques have problems such as the effect of expanding the range of output improvement by utilizing the intake inertia effect is small and insufficient, and widening the range of change requires a complicated mechanism. It is hoped that the structure will provide greater tuning over a wider range.

For example, in a case where only the length of the intake passage is changed, the tuning range itself is narrow, and even if the tuning is in a tentative state, the optimum tuning conditions can be set to obtain the maximum intake inertia effect at that engine speed. It does not necessarily match. Similarly, when changing the length and area of the intake passage to obtain synchronization with the air column frequency at each engine speed, there are various length and area values that satisfy the tuning conditions at a given engine speed. However, not all conditions result in a good increase in filling efficiency.

In other words, the intake inertia effect uses air column vibration to increase the pressure at the intake port at the end of the intake stroke to improve filling efficiency, but this filling efficiency is dependent on the size of the intake passage area (diameter) itself. However, when setting a passage area with low filling efficiency, even if you change the length of the intake passage and improve the filling efficiency due to the intake inertia effect, the filling efficiency will basically be low. Even if it is improved by the intake inertia effect, it is not possible to obtain a good output improvement effect as a whole, and it is not possible to make the most of the intake inertia effect by simply matching the intake inertia tuning conditions like this. It is something.

(Object of the Invention) In view of the above circumstances, the present invention focuses on the intake flow velocity to expand the inertia tuning region by changing the length of the intake passage. It is an object of the present invention to provide an engine intake device whose length and area are changed to improve output.

(Structure of the Invention) The intake device of the present invention makes the length of the intake passage variable and the area of the intake passage, and adjusts the average intake flow velocity sucked into the intake port to an optimum value of 40 to 60 m/s, which increases the volumetric efficiency. The intake passage area is set according to the engine rotation speed so as to maintain it within the range, and the passage area is changed to the above-mentioned set passage area based on the detected engine rotation speed, and the intake passage area corresponding to the engine rotation speed is changed to the above-mentioned set passage area based on the detected engine rotation speed. Based on the setting of the passage area, set the intake passage length under which the engine rotation speed and air column frequency are synchronized and obtain the intake inertia effect, and then set the above-mentioned set passage length based on the detected engine rotation speed. This is characterized in that the length of the intake passage is changed so that

(Effects of the Invention) According to the present invention, by changing the intake passage length and intake passage area, the inertial tuning range is expanded and the output is improved in each region. The intake passage area is set according to the engine speed so that it is within the optimum range of 60 m, and the intake passage area is changed to the above set passage area based on the detected engine speed. In addition to ensuring conditions for good filling efficiency, the length of the intake passage is such that the engine rotation speed and air column frequency are synchronized under the above conditions, and the intake inertia effect is obtained. By setting the intake passage length to the above-mentioned setting passage length based on the detected engine speed, the maximum intake inertia effect is always obtained and the output is effectively improved. It is something that can be achieved.

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

Embodiment 1 FIG. 1 shows a sectional front view of essential parts of a multi-cylinder engine equipped with an intake device.

An intake passage 3 that communicates with the combustion chamber 2 of each cylinder of the engine 1 is branched downstream of the surge tank 5 and is connected to each cylinder independently, and communicates with the combustion chamber 2 from the cylinder head 6 through an intake port 7. However, a fuel injection nozzle 8 is disposed in the middle.

Further, the intake passage 3 includes a passage length variable means 9 having a cylindrical member 11 slidably installed in the connecting portion with the surge tank 5, and an intake port 7.
Passage area changing means 10 including a moving member 12 provided between the vicinity and the inside of the cylindrical member 11
is installed. The passage length changing means 9 changes the length of the intake passage by moving the cylindrical member 11 with an actuator 13, while the passage area changing means 10 moves the moving member 12 with an actuator 14. The actuators 13 and 14 are driven and controlled by control signals from a control means (control unit). This control means 15 receives an engine speed signal from a speed sensor 16 and a load signal from a load sensor 17, and changes and adjusts the length and area of the intake passage in response to fluctuations in engine speed in a high load range. It is something.

The surge tank 5 side end 12 of the movable member 12 is rotatably attached, and its tip is connected to the cylindrical member 1.
1 inner surface, this cylindrical member 1
It is configured to increase/decrease the area of the passage through which intake air passes while allowing the sliding movement of 1. In addition, in FIG. 1, 19 is an intake valve, 20 is a cylinder block, and 21 is a piston.

The control means 15 increases the intake passage area by driving the passage area changing means 10 in accordance with the increase in engine speed, and keeps the average intake flow velocity at the intake port 7 substantially constant so that it is within the optimum flow velocity range. At the same time, the length of the intake passage is changed and adjusted by driving the passage length variable means 9 so that the engine rotational speed and the air column frequency are synchronized in this intake passage area and an intake inertia effect is obtained. This change is greatly affected by the change in passage area, but basically the passage length is shortened in response to an increase in engine speed. In addition, in reality,
Since the passage area and length can be set in advance in accordance with the engine speed, the control means 15
adjusts both at the same time.

The intake inertia tuning condition is such that the intake period corresponding to the engine speed is approximately equal to the period of air column vibration corresponding to the length and area of the intake system, and the pressure at the intake port 7 increases immediately before the intake valve 19 closes. There are an infinite number of combinations of intake passage length and area to obtain such tuning conditions.
The results of determining the relationship between the volumetric efficiency and the average flow velocity in the intake passage when the length and area are changed at the same time are shown in the fifth section.
As shown in the figure. As can be seen from FIG. 5, when the passage length and area are changed at each engine speed, there is an optimum flow rate A at which the volumetric efficiency is maximized.

Therefore, the control means 15 outputs a control signal to the actuator 14 of the passage area changing means 10 to change the passage area so that the intake air flow velocity is maintained within the range of the optimum flow velocity A against fluctuations in engine speed. At that point, in order to obtain intake inertia tuning conditions, the passage length is calculated for the passage area, and a control signal is output to the actuator 13 of the passage length variable means 9, and the intake inertia is adjusted at each engine speed. It makes maximum use of the inertial effect to obtain large volumetric efficiency and improve output.

In addition, in FIG. 5, the characteristic a shown by the broken line is
When the aisle area is fixed at a certain value,
It shows the synchronized state obtained by changing the passage length, and when the engine speed is high, the average intake flow velocity is within the range of the optimum flow velocity A (the passage area is relatively wide), and good volumetric efficiency is achieved. is obtained, but
As the rotational speed decreases, the intake flow rate decreases, and even if the passage length is changed, the volumetric efficiency will not improve much. In this case, as the engine speed decreases, the passage area is reduced to increase the intake flow velocity to within the optimal range, and the passage length is changed to obtain a synchronized state in combination with the reduced passage area. It is controlled as follows.

Further, the value of the above-mentioned optimum intake flow rate varies depending on the type of engine, etc., but as an example, it is 40 to 60 m/s, preferably 50 m/s. On the other hand, the tuning condition that maximizes the intake inertia effect is that, where the intake period is ts and the air column frequency is fs, the intake period ts and the air column vibration period 1/fs are approximately equal, for example, 0.9<ts×fs< 1.1.

Embodiment 2 FIG. 2 is a sectional front view of essential parts of a multi-cylinder engine equipped with an intake system of this embodiment, and FIG. 3 is a sectional view taken along the line - in FIG. Note that even if the structure is different from that in FIG. 1, some parts with the same names are given the same reference numerals.

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 independently to each cylinder, and is connected to the combustion chamber 2 of each cylinder for fuel injection. A nozzle 8 is provided.

The surge tank 5 is formed by a casing 22 and a cylindrical rotating member 23 rotatably installed inside the casing 22, and includes a passage length variable means for changing the passage length of the intake passage 3. 9 are configured. This casing 22 is the engine 1
An intake manifold fastened to the cylinder head 6 of the casing 22 is formed, and extended portions of the intake passages 3 connected to each cylinder are formed along the circumferential direction of the casing 22. In addition, the rotating member 23
The internal space is an expansion chamber downstream of the throttle valve 4, in other words, it constitutes a substantial surge tank as an intake air holding space, and an opening 23a is provided at the center of one end surface. It communicates with the upstream intake passage 3 provided with the throttle valve 4 and serves as an intake inlet. Each intake passage 3 is made independent for each cylinder by being in contact with the inner wall surface of the intake passage 3 for each cylinder. A communication port 23b on the outlet side communicating with the intake passage 3 for each cylinder is provided on the circumferential surface of the rotating member 23, and the communication position between the internal space and the intake passage 3 changes in accordance with the rotational position of the rotating member 23. However, as a result, the length of the intake passage 3 from the surge tank 5 to each cylinder is made variable.

A casing 22 is provided on the other end surface of the rotating member 23.
A shaft portion 23c that projects outwardly is connected to the casing 22 around the shaft portion 23c and the opening 23a.
A gear 26 fixed to the output shaft of the motor 25 is engaged with an input gear 24 fixed to the end of the shaft portion 23c. A driving means 27 is configured to change the length of the intake passage. The motor 25 is a control means 15 (control unit).
The drive is controlled by control signals from.

Further, in the intake passage 3 downstream of the surge tank 5, a regulating valve 28 for changing the passage area and changing the intake flow rate is disposed at a position close to the intake port 7, thereby forming passage area changing means 10. The regulating valve 28 is connected to an operating rod 29 and is configured to rotate as the operating rod 29 is operated by an actuator 30. The actuator is also driven and controlled by a control signal from the control means 15.

The control means 15 receives the engine speed signal from the rotation speed sensor 16 and the load signal from the load sensor 17 as in the previous example, and the control means 15 adjusts the length of the intake passage in response to fluctuations in the engine speed. The driving means 27 of the passage length variable means 9 for changing the intake passage length and the passage area changing means 10 for changing the intake passage area are driven and controlled to keep the intake flow velocity substantially constant within the optimum range, and to maintain the intake passage 3 approximately constant. The intake passage area and the intake passage length are adjusted to values where the air column vibration frequency and the period of the intake period based on the engine rotational speed are synchronized and the intake inertia effect is maximized.

The control of the passage length variable means 9 and the passage area changing means 10 by the control means 15 in this embodiment is basically the same as in the previous example, but in the previous example, the passage area changing means 10 controls the passage length changing means 9 and the passage area changing means 10. Whereas the passage area of the entire intake passage was changed, in this example, the passage area of only a part of the intake passage 3 near the intake port 7 is changed; The effect on the air column frequency is smaller than the previous example, so
Even if the regulating valve 28 of the passage area changing means 10 is operated in order to obtain the optimum intake flow velocity with respect to fluctuations in the engine speed, the variation in the tuning condition of the intake inertia is small, and it is possible to obtain the maximum intake inertia effect. Adjustment to the synchronized state is mainly performed by changing the path length using the path length variable means 9. Therefore, even if the passage length is changed to obtain a synchronized state by operating the passage length variable means 9, and the intake flow rate is adjusted by changing the passage area, the synchronized state will hardly change.

Embodiment 3 This example is shown in FIG. 4, and is equipped with the same passage length changing means 10 as in the previous example, but a movable member 31 disposed in the intake passage 3 downstream of the surge tank 5 is moved through a link 32. actuated by the actuator 33,
A passage area changing means 10 is provided which changes the passage area not only in the vicinity of the intake port 7 but also in the upstream portion thereof. In this example, as in the first embodiment, the intake By changing the air column vibration as the flow velocity changes, the tuning range is expanded and output can be improved over a wider range of engine speeds due to the large intake inertia effect.

The rest of the structure is the same as in the previous example, and the same structures are given the same reference numerals and their explanations will be omitted.

Therefore, in each of the above embodiments, the intake flow velocity is maintained in the optimum range A by changing the passage area, and the passage length is varied to obtain the intake inertia effect, so that the intake inertia effect is maximized. It can be used to improve charging efficiency, and it is possible to obtain a large intake inertia effect over a wide range and improve output. Particularly in the low rotation range, the area of the intake passage can be reduced to maintain the intake flow velocity and improve the combustion performance within the combustion chamber.

Further, in the second and third embodiments, the intake passage extension part in which the passage length variable means 9 for changing the intake passage length is formed around the surge tank 5, and the rotating member 23 that rotates along the intake passage extension part. With this configuration, the entire structure can be made compact, the structure can be simplified, and reliable operation can be ensured.

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

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view of a main part of an engine having an intake system according to a first embodiment of the present invention, FIG. 2 is a front cross-sectional view of a main part of an engine having an intake system according to a second embodiment, and FIG. is a sectional view taken along the - line in Fig. 2, Fig. 4 is a sectional front view of main parts of an engine having an intake system according to the third embodiment, and Fig. 5 is a sectional view taken when the length and area of the intake passage are changed at the same time. FIG. 3 is a characteristic diagram showing the relationship between volumetric efficiency and average flow velocity in an intake passage. DESCRIPTION OF SYMBOLS 1... Engine, 3... Intake passage, 5... Surge tank, 7... Intake port, 9... Passage length variable means, 10... Passage area changing means, 15... Control means.

Claims (1)

[Claims] 1. A passage length variable means for varying the length of the intake passage leading to the cylinder is provided, and a passage area changing means for changing the passage area of the intake passage at least near the intake port is provided, and the average intake flow velocity taken into the intake port is The intake passage area is set according to the engine rotation speed so as to maintain the intake passage area within the optimum range of 40 to 60 m/s where the volumetric efficiency is high, and the passage area is adjusted to the above-mentioned set passage area based on the detected engine rotation speed. Assuming that the changing means is actuated and the intake passage area is set in accordance with the engine rotation speed, the intake passage length is such that the engine rotation speed and the air column vibration frequency are synchronized under that condition and an intake inertia effect is obtained. 1. An intake system for an engine, comprising: a control means for controlling the operation of the intake passage length variable means so that the length of the intake passage is set to the set passage length based on the detected engine rotational speed.