JPH0689663B2 - Engine intake system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an engine intake device that improves output by a dynamic effect of intake air and suppresses knocking.

(Prior Art) Conventionally, in an intake device of an engine, it is used that a pressure wave generated with the start of intake is reflected at the opening end to the atmosphere or the volume chamber on the upstream side of the intake passage and returned to the intake port direction. There is a system in which the reflected wave reaches the intake port just before the closing of the intake valve to increase the intake pressure, so that the charging efficiency of intake air is increased by the so-called inertia effect of intake air. When attempting to use such an output enhancement technology that utilizes the dynamic effect of intake air, if the intake path is constant, the vibration cycle of the pressure wave generated in the intake passage and the intake valve opening / closing cycle match and inertia The effect is enhanced only in a specific speed range.

Therefore, as seen in JP-A-56-115819,
The length of the intake passage is changed according to the engine speed. For example, the intake passage for each cylinder is branched at the upstream portion to form a long passage and a short passage, and the upstream ends of these passages are In addition to opening to the volume chamber, etc., an opening / closing valve is provided in a short passage, and by opening this opening / closing valve in the high speed range, the effective length of the intake passage is shortened. An intake device designed to enhance the effect has also been proposed.

As described above, in the case where the dynamic effect of intake air is effectively used, knocking is likely to occur due to the improvement of the charging efficiency, and particularly in the case where the supercharger is provided, the charging efficiency is further improved, and thus knocking is prevented. It is likely to occur. Since the occurrence of knocking adversely affects the durability of the engine and the like, a technique is known in which the occurrence of knocking is detected by a knock sensor or the like, and the ignition timing is retarded to suppress the occurrence of knocking. ing.

However, the knocking suppression by retarding the ignition timing reduces the output while keeping the charging efficiency and the fuel supply amount as they are, and the fuel supply amount must be increased to obtain the same output. Will be reduced.

(Object of the Invention) In view of the above circumstances, the present invention enhances intake charging efficiency by utilizing the dynamic effect of intake air from low speed range to high speed range, and suppresses knocking without lowering fuel efficiency. It is an object of the present invention to provide an intake system for such an engine.

(Structure of the Invention) The intake system of the present invention is provided with an intake switching mechanism that selects a plurality of paths in accordance with the engine speed in order to match the dynamic effect of intake air in response to changes in the engine speed. It is characterized in that knocking detection means for detecting occurrence of knocking from abnormal vibration of the engine is provided, and control means for operating the intake switching mechanism in a direction in which the dynamic effect is reduced when knocking occurs.

(Effect of the Invention) According to the present invention, the dynamic effect of intake air is effectively utilized by the operation of the intake air switching mechanism in a wide range of engine speeds, high charging efficiency is obtained from the low speed region to the high speed region, and the output performance is improved. Can be improved.

In addition, when knocking occurs, the intake switching mechanism is activated to stop the action of increasing the filling amount due to the dynamic effect of intake air.
By reducing the intake charge amount and suppressing the occurrence of knocking, the adverse effect due to the occurrence of knocking can be improved. Further, since the suppression of knocking is obtained by the reduction of the filling amount itself, the fuel supply amount also decreases with the reduction of the filling amount, so that there is no reduction in the fuel consumption rate due to the suppression of knocking, and the ignition timing is retarded. On the other hand, it is possible to maintain a good fuel consumption rate. Furthermore, the ignition timing can be set to a timing at which a more optimal output can be obtained, and good combustion performance can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional front view of an engine equipped with an intake device of this embodiment,
FIG. 2 is a schematic plan view.

The engine of this embodiment is a four-cylinder four-cycle engine, and four cylinders 4a to 4d are formed in an engine body 1 including a cylinder block 2 and a cylinder head 3. A combustion chamber 6 is formed above the piston 5 in each of the cylinders 4a to 4d, and an intake port 7 and an exhaust port 8 are opened in the combustion chamber 6, and a predetermined predetermined value is set in the ports 7 and 8 by a valve mechanism 11. It is equipped with an intake valve 9 and an exhaust valve 10 that open and close at the timing.

Independent intake passages 12a to 12d for each cylinder, which are independent of each other, communicate with the intake ports 7 of the cylinders 4a to 4d. The upstream ends of these independent intake passages 12a to 12d are connected to a first volume chamber 13 having a certain capacity, and these independent intake passages 12a to 12d are provided with midstream points of these independent intake passages 12a to 12d.
The 2nd volume chamber 14 which connects 12a-12d mutually is connected. As a result, two long and short intake passages that connect the cylinders 4a to 4d and the volume chambers 13 and 14 are formed.

In this embodiment, in order to make the intake system compact, the tank 15 interposed in the intake system is divided by the partition wall 16 to divide the first volume chamber 13 and the second volume chamber 14 into the tank 15. And each independent intake passage 12a is formed at the lower end of the second volume chamber 14.
The communication hole 17 branched from the middle part of ~ 12d is opened, and each independent intake passage is provided on the upstream side of the communication hole 17.
12a to 12d are curved, and their upstream ends are opened to the side of the first volume chamber 13. In addition, each of the above independent intake passages 12a-1
The upstream curved portion 2d is integrally formed using the wall portion of the second volume chamber 14 of the tank 15.

An opening / closing valve 19 (intake switching mechanism) for switching the intake path is provided in a communication hole 17 between the second volume chamber 14 and each of the independent intake passages 12a to 12d. Each of the on-off valves 19 is integrally connected to the rotary shaft 19a, and the actuator 20 (not shown in FIG. 2) of the control means 21 is connected to the end of the rotary shaft 19a so that the cylinders are linked. Then it is opened and closed. This on-off valve 19 is basically controlled to close in the low speed range where the engine speed is lower than the set value and to open in the high speed range where the engine speed is higher than the set value in order to improve the dynamic effect in the high load range. To be done.

An upstream intake passage 26 is connected to one end of the first volume chamber 13, and a throttle valve 27 is arranged in the intake passage 26, and an upstream end thereof has a turbocharger 22. Is connected to the blower 22a, and is connected to an air cleaner via an air flow meter (not shown). Above turbocharger
An exhaust manifold 23 communicating with the exhaust port 8 is connected to the turbine 22b of 22 and the blower 22a is rotationally driven via the turbine 22b by the introduction of exhaust gas. Further, a fuel injection valve 29 connected to a fuel passage 28 is arranged near the downstream end of each of the independent intake passages 12a to 12d.

A control signal from the engine control unit 37 (ECU) is output to the actuator 20 in the control means 21, and its operation is controlled according to the engine speed and knocking. The engine control unit 37 receives an engine speed detection signal from a speed sensor 38, and knocking detection means 39.
A knocking detection signal from the (knock sensor) is input. The knocking detection means 39 detects the vibration of the engine body 1, and detects the occurrence of abnormal vibration of the engine as occurrence of knocking.

The opening and closing of the on-off valve 19 by the control means 21 is performed at a set value of the engine speed, and the on-off valve 19 is closed at a low speed range below this set value and the on-off valve at a high speed range above the set value.
It is to open 19. Further, when knocking occurs, the on-off valve 19 is operated in a direction in which the charging efficiency is lowered, and the on-off valve 19 is opened in the low speed range and the on-off valve 19 is closed in the high speed range. The opening / closing operation of the opening / closing valve 19 according to the engine speed as described above may be performed at least during a high load when output is required, and when the load is low, the opening / closing valve 19 does not depend on the engine speed.
19 may be kept closed or open.

In the apparatus of the above-described embodiment, when the engine speed is in the low speed range below the set value, the on-off valve 19 is closed and the communication between the independent intake passages 12a to 12d and the second volume chamber 14 is cut off. The cylinders 4a to 4d are connected to the first volume chamber 13 via relatively long passages extending over the entire length of the independent intake passages 12a to 12d.

Therefore, the pressure wave generated in the intake stroke of each cylinder 4a-4d is propagated to the first volume chamber 13 through each independent intake passage 12a-12d,
The cylinders 4a to 4d are reflected in the first volume chamber 13 to generate intake pressure vibrations in the independent intake passages 12a to 12d. Therefore, the independent intake passages 12a to 12d between the cylinders 4a to 4d and the first volume chamber 13 are formed.
Each cylinder 4a ~ in the rotation range on the low speed side where the cycle of the natural vibration of the intake system that occurs inside and the intake valve opening / closing cycle match
The pressure acting on 4d is increased at the end of the intake stroke, and the charging efficiency is improved. In this low speed range, knocking detection means
When the occurrence of knocking is detected by 39, the opening / closing valve 19 which is closed as described above is opened.

On the other hand, when the engine speed is in the high speed range above the set value, the on-off valve 19 is opened and the independent intake passages 12a to 12d and the second volume chamber 14 are communicated with each other by the communication hole 17, and each cylinder 4a
.About.4d are connected to the second volume chamber 14 through the relatively short passage lengths of the independent intake passages 12a to 12d between the second volume chamber 14 and the second volume chamber 14, respectively. At this time, the intake air flows from the first volume chamber 13 into the independent intake passage.
It is supplied by the independent intake passages 12a to 12d from the independent intake passages 12a to 12d of the other cylinders through the second volume chamber 14 communicating with the independent intake passages 12a to 12d of the other cylinders.

In this state, the pressure wave generated in the intake stroke is reflected by the second volume chamber 14 and the passage length used for propagating the pressure wave and the reflected wave is shortened, so that the intake inertia effect is achieved in the high speed range. At the same time, the pressure wave propagated from the other cylinders also effectively acts in this operating range to improve the charging efficiency. In this high speed range, when the knocking detection means 39 detects the occurrence of knocking, the open / close valve 19 that is open as described above is closed.

FIG. 3 shows the relationship between the engine speed and the torque. Curve A is a fully open line when the on-off valve 19 is closed, and curve B is a fully open line when the on-off valve 19 is open. The engine speed No. corresponding to the intersection of the curves A and B is the set value No. for operating the actuator 20 to open / close the on-off valve 19, and the engine speed No. is closed on the lower speed side and opened on the higher speed side. It is intended to improve the output by increasing the intake charging efficiency in the entire rotation range. Further, knocking occurs in the knock zone I on the low speed side, and particularly in the knock zone II on the high speed side in the case where the turbocharger 22 is provided, the knocking II at the high speed is caused by the piston 5 There is a problem of causing melting damage of.

FIG. 4 shows the relationship between the engine speed and the charging efficiency due to the opening / closing of the on-off valve 19. The characteristics A'of the charging efficiency when the on-off valve 19 is closed and the characteristics B'when the valve is open. ,
In the low speed range of less than the set value No, the filling efficiency is higher in the low speed range of less than the set value No. On the other hand, in the high speed range of the set value No or higher. The filling efficiency is higher when the on-off valve 19 is opened.

Correspondingly, lowering the charging efficiency is similar to delaying the ignition timing, and knocking is less likely to occur by lowering the flame speed. The opening / closing valve 19 is opened / closed in a direction to reduce the dynamic effect of the intake air so as to reduce the charging efficiency that is increasing with the physical effect, thereby suppressing the occurrence of knocking.

As the control method by the control means 21, the closed state is completely switched to the open state, or the open state is completely switched to the closed state, and the knocking detection means 39 does not detect the occurrence of knocking. Adjust the opening to maintain the filling efficiency near the knocking limit,
What keeps the filling efficiency as high as possible is appropriately adopted as necessary.

Although the example of the engine provided with the supercharger is shown in the above embodiment, the engine provided with the supercharger increases the exhaust gas amount as the charging efficiency is improved due to the dynamic effect of intake air. As a result, the supercharging pressure rises and the charging efficiency further rises, so knocking is particularly likely to occur, and knocking due to abnormal combustion in the high-speed range is also likely to occur, so knocking measures are particularly required. However, it goes without saying that the present invention can be applied to an engine that does not include a supercharger. Further, as the supercharger, other than the turbo supercharger, other supercharger can be used, and the supercharge by the supercharger and the natural intake may be used together.

Further, as a plurality of intake passages for obtaining the dynamic effect of intake air, in addition to the one in which the length of the intake passage is changed and the communication with the intake passages of other cylinders is switched as in the above embodiment, It is possible to adopt a plurality of intake passages by a structure for changing various dynamic effects such as a change of the intake passage area or a volume of the intake volume chamber, or a combination structure thereof, and the dynamic effect can be changed depending on the engine speed. The intake switching mechanism that performs switching operation so as to improve is operated so as to reduce the dynamic effect when knocking occurs. Further, the upstream end of the intake path for obtaining the dynamic effect of intake air communicates with the intake volume chamber or the atmosphere opening.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional front view of an engine equipped with an intake device according to an embodiment of the present invention, FIG. 2 is a schematic plan view thereof, and FIG. 3 is a torque characteristic according to engine speed. FIG. 4 is a characteristic diagram showing the characteristic of charging efficiency according to the engine speed. 1 ... Engine body, 4a-4d ... Cylinders 12a-12d ... Independent intake passage 13 ... First volume chamber, 14 ... Second volume chamber 19 ... Open / close valve (intake switching mechanism) 20 ... Actuator, 21 ... Control means 37 ... Engine control unit 38 ... Rotation speed sensor 39 ... Knocking detection means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Kazushi 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-61-106917 (JP, A)

Claims (1)

[Claims] 1. An intake air switching system in which a plurality of intake paths are provided to connect one cylinder to an intake volume chamber or an atmospheric opening, and the plurality of paths are selected so as to increase the dynamic effect of intake air according to the engine speed. In an engine intake device provided with a mechanism, knocking detection means for detecting occurrence of knocking from abnormal vibration of the engine is provided, and control means for operating the intake switching mechanism in a direction in which the dynamic effect is reduced when knocking occurs. An engine air intake device characterized by being provided.