JPH0754093B2 - Engine intake system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an engine, which utilizes the dynamic effect of intake air to improve the charging efficiency.

(Prior Art) Conventionally, various intake devices for an engine have been known in which the intake charging efficiency is increased by utilizing the fluctuation of the intake pressure accompanying the operation of the engine. For example, in the device disclosed in Japanese Patent Laid-Open No. 173520/1984, the intake manifold is divided into a plurality of cylinder groups whose intake orders are not adjacent to each other, and the intake passage is joined upstream of the intake manifold collecting portion. The intake manifold collecting portions and the intake passages between the intake manifold collecting portion and the merging portion are communicated with each other through the volume portions, and the first and second connecting portions are connected to each other. The respective on-off valves are provided, and the on-off control of these valves is performed according to the operating conditions of the engine. According to this device, the reflection position of the intake pressure wave is switched stepwise between when both the on-off valves are closed, when only the second on-off valve is opened, and when the first on-off valve is opened. Since the substantial length of the passage related to the cycle of pressure oscillation changes, the dynamic effect can be enhanced in each of the low speed, medium speed, and high speed regions to improve the filling efficiency.

However, in such a conventional device, the intake passage (the intake manifold and the intake passage on the upstream side thereof) that serves as a flow path for supplying intake air introduced from the outside to each cylinder is
Since the structure for imparting the dynamic effect as described above is incorporated, the intake system becomes complicated, the length of the intake passage is restricted, and the layout of the intake system is restricted. Moreover, if only the intake passage for supplying intake air has a dynamic effect, the degree of freedom in adjusting the dynamic effect according to the required operating range and the degree of improvement in the charging efficiency are limited.

(Object of the invention) In view of such circumstances, the present invention can relatively simplify the structure of the intake system, and can increase the degree of freedom in designing the intake system and adjusting the dynamic effect. While
(EN) An intake device for an engine capable of further enhancing the dynamic effect of intake air and improving the charging efficiency.

(Structure of the Invention) In addition to the intake port that supplies intake air to the combustion chamber,
An auxiliary intake port that is opened during the intake stroke and an intake expansion chamber that communicates only with this auxiliary intake port via a communication passage are provided, and the natural frequency of the air column in the communication passage is within the practical rotational speed range. The passage length of the communication passage is set to be an integral multiple of the number of intakes of one engine cylinder per unit time at a specific engine speed.

With this configuration, a pressure wave resonating within the practical rotational speed range is generated in the communication passage between the auxiliary intake port and the intake expansion chamber, apart from the intake system that originally supplies the intake air, and the resonance pressure in this communication passage is generated. The waves enhance the suction power of the engine and enhance the dynamic effect.

(Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention. In this embodiment, the device of the present invention is applied to a 4-cylinder 4-cycle reciprocating engine. In these figures, in each cylinder 2 of the engine body 1, a combustion chamber 4 is provided above the piston 3.
Are formed. In the combustion chamber 4, an intake port 6 that is opened and closed by an intake valve 5 to supply intake air to the combustion chamber 4,
An exhaust port 8 opened and closed by the exhaust valve 7 is opened, and in addition to these, an auxiliary intake port 9 for increasing the dynamic effect of intake is opened. This auxiliary intake port 9
It is designed to be opened during the intake stroke by the auxiliary intake valve 10.

The intake port 6 of each cylinder 2 is connected to an intake passage 11 for each cylinder, and the intake passage 11 for each cylinder is connected to a surge tank 13 into which outside air is introduced from an upstream intake passage 12. An air cleaner 14, an air flow meter 15, and a throttle valve 16 are arranged in the upstream side intake passage 12,
11 is equipped with a fuel injection valve 17. Further, the exhaust port 8 is connected to the exhaust manifold 18.

On the other hand, the auxiliary intake port 9 is connected to the intake expansion chamber 21 provided separately from the surge tank 13 via a communication passage 22. The intake expansion chamber 21 is closed to the atmosphere,
Only the auxiliary intake port 9 communicates with the communication passage 22.

The passage length of the communication passage 22 is such that the engine speed at which the natural frequency of the air column in the communication passage 22 is an integral multiple of the number of intakes for each cylinder of the engine per unit time is within the practical rotation speed range. Is set to. That is, the number of suctions is determined by the engine speed, and the natural frequency of the air column in the communication passage 22 is related to the passage length of the communication passage 22,
At a specific engine speed in response to a request within a practical speed range, the natural frequency is an integral multiple of the suction frequency (for example, 2
Double or quadruple)
The passage length of the communication passage 22 is set.

In addition, the communication passage 22 is provided with this communication passage depending on the operating state.
A shutter valve 23 that opens and closes 22 is provided. The shutter valve 23 is a control unit that receives signals from the engine speed sensor 24 and the throttle opening sensor 25.
26 is controlled via a drive means such as a three-way solenoid valve 27 and a negative pressure responsive actuator 28, and requires a low rotational speed range or a dynamic effect where the dynamic effect due to the pressure fluctuation of the communication passage 22 cannot be obtained. In the low load range, the communication passage 22 is closed.

The operation of such an intake device will be described with reference to FIGS.

FIG. 3 shows the pressure fluctuation corresponding to the opening operation (lines A and B) of the intake valve 5 and the auxiliary intake valve 10 in the intake stroke at a specific engine speed. In this figure, IO and
IC represents the opening timing and closing timing of the intake valve 5, and TDC and BDC represent the top dead center and the bottom dead center of the piston 3. Explaining the pressure fluctuation shown in this figure, with the operation of the piston 3, the intake pressure in the cylinder and near the intake port 6 decreases (the negative pressure increases) until the middle of the intake stroke where the volume change rate is large.
However, since the pressure gradually rises in the middle of the intake stroke, the basic supply pressure waveform near the intake port 6 becomes as shown by the line C. On the other hand, a negative pressure is generated in the vicinity of the auxiliary intake port 9 in the middle of the intake stroke due to the pressure change in the cylinder.
Is propagated, is inverted into positive pressure in the intake expansion chamber 21, and is reflected, so that pressure oscillation occurs in the communication passage 22. When this pressure vibration resonates with the pressure fluctuation in the cylinder, a large pressure wave indicated by the line D is obtained near the auxiliary intake port 9. In this resonance state, due to the influence of the pressure wave (line D), the negative pressure in the cylinder in the middle of the intake stroke increases and the suction force increases, so the intake pressure wave is strengthened (line E), and as a result, the end of the intake stroke. The degree of increase in the pressure near the intake port is also increased, and the intake supply amount from the intake port 6 increases.

FIG. 4 and FIG. 5 show two kinds of states in which the effect of the above resonance can be obtained. That is, as shown in FIG. 4, the natural frequency of the air column of the communication passage 22 is twice the number of inhalations per unit time (the period T _{1 of the} natural oscillation is 1/2 of the inhalation period T ₀ ).
In this case, the pressure wave (line D ₁ ) in the communication passage 22 resonates and the intake pressure wave (line C) is strengthened. Further, as shown in FIG. 5, the natural frequency of the air column of the communication passage 22 is four times the number of inhalations per unit time (the period T _{2 of the} natural vibration is equal to the inhalation period T ₀ .
Even in the case of 1/4), the pressure wave (line D ₂ ) in the communication passage 22 is in a resonance state and the intake pressure wave (line C) is strengthened.

If the effective passage length of the communication passage 22 is le, the engine speed is n, and the sound velocity is a, then le = (180/360) x (60 / n) x (a / 2). The state of Fig. 4 is obtained, and if le = (180/360) x (60 / n) x (a / 2) x (1/2) ..., the state of Fig. 5 is obtained. Therefore, 5000-7000
In order to obtain a dynamic effect at an engine speed of rpm, the sound velocity a is set to 360 (m / s), and the effective passage length le of the communication passage 22 is set to 1.08 to 0.77 (m) based on the above formula. Alternatively, based on the above formula, set the effective passage length le of the communication passage 22 to 0.54 to 0.39.
(M), and the actual length of the communication passage 22 may be set to the effective passage length minus the opening end correction amount. Moreover, if the length of the communication passage 22 is set so that the dynamic effect according to the state of FIG. A dynamic effect can be obtained by the state of FIG.

In this way, the dynamic effect is enhanced by the resonance of the pressure wave in the system in which the auxiliary intake port 9 and the intake expansion chamber 21 are connected by the communication passage 22. Especially, since the system that causes the above resonance is provided separately from the intake system for the original intake supply,
The length and shape of the intake passage 11 in the original intake system are not restricted, and the original intake system can be designed relatively freely in accordance with the layout and the like. Further, even when the intake passage 11 is set so that the basic intake pressure oscillation occurring in the intake passage 11 is synchronized with the intake cycle at an appropriate engine speed, the communication passage 22 separates from the desired engine. Since it can be set to give the effect of resonance at the number of revolutions,
Both systems synergistically enhance the dynamic effect, or the communication passage 22 in the rotational speed range where the dynamic effect of the original intake system is small.
Adjustments such as generating resonance in the interior to supplement the dynamic effect can be optionally performed, and the degree of freedom in adjusting the dynamic effect is increased.

FIG. 6 shows a second embodiment of the present invention. In this embodiment,
The substantial passage length of the intake passage 11 for each cylinder from the surge tank 13 to the intake port 6 is variable. That is,
The intake passage 11 has a relatively long passage portion branched into two branches at the upstream side thereof and connected to the surge tank 13 respectively.
11a and a short passage portion 11b are formed, and the short passage portion 11b is formed.
A shutter valve 30 for changing the intake passage length is provided in the.
Reference numeral 31 is a negative pressure responsive actuator that opens and closes the shutter valve 30, and reference numeral 32 is a three-way solenoid valve that receives a signal from the control unit 26 and controls the supply of negative pressure to the actuator 31. Further, the auxiliary intake port 9, the communication passage 22 connected to the auxiliary intake port 9, the intake expansion chamber 21 and the like have the same structure as in the first embodiment.

Then, by the control unit 26, the communication passage 22
The shutter valve 23 and the intake passage length changing shutter valve 30 are controlled respectively, and, for example, as shown in FIG.
The shutter valve 23 of 22 is opened in an appropriate operating range Sa other than the low load range in the low rotation range, while the shutter valve 30 for changing the intake passage length is used.
Is opened in an operating range Sb on the higher rotation side than a predetermined rotation speed.

According to the device of the second embodiment, on the intake passage 11 side for supplying intake air, the shutter valve 30 is operated in the low rotation speed region.
Is closed to substantially lengthen the intake passage, and in the high rotation region, the shutter valve 30 is opened to substantially shorten the intake passage length, so that the low rotation side is caused by the pressure oscillation itself of the intake passage. The dynamic effect is enhanced. Also in this case, in addition to the intake passage 11, the communication passage 22 between the auxiliary intake port 9 and the intake expansion chamber 21 may be set so as to have a dynamic effect at a predetermined engine speed. It is possible and the degree of freedom in adjusting the dynamic effect is increased.

FIG. 8 shows a third embodiment of the present invention. In this embodiment,
In the communication passage 22 between the auxiliary intake port 9 and the intake expansion chamber 21, a rotary timing valve 34 that opens and closes in synchronization with the engine is provided. This timing valve 34
The opening timing and the closing timing of the auxiliary intake port 9 are adjusted substantially, the opening timing and the closing timing are later than those of the auxiliary intake valve 10, and the opening / closing timing can be adjusted by a phase adjusting means (not shown). Has become. Then, as shown in FIG. 9, the actual opening timing V ₀ of the auxiliary intake port 9 is advanced to lengthen the actual opening period Vt on the high engine speed side, and the actual opening timing V ₀ is delayed on the low engine speed side. The timing valve 34 is controlled so as to shorten the substantial open period Vt.

According to this structure, the phase of the pressure wave in the communication passage 22 is adjusted according to the engine speed, so that the dynamic effect can be enhanced to some extent at a speed other than the speed at which resonance occurs, and the pressure is rapidly increased at relatively low speeds. Intake pressure wave can be strengthened by causing various pressure fluctuations.

FIG. 10 shows a fourth embodiment of the present invention. 2 in this example
The device of the present invention is applied to a rotary piston engine of a cylinder, and a rotor housing 41 of each cylinder is provided with a substantially triangular rotor 42 that makes a planetary rotational motion.
Thus, three working chambers 43 corresponding to the combustion chamber are defined. Further, the side housing 44 of each cylinder is formed with an auxiliary intake port 46 in addition to the intake port 45 for supplying intake air, and these ports 45, 46 are adapted to be opened and closed as the rotor 42 rotates. There is.

The intake port 45 communicates with a surge tank 47 into which the outside air is introduced via an intake passage 48, and the auxiliary intake port 45
46 is connected via a communication passage 50 to an intake expansion chamber 49 that is closed from the outside air. The other parts equivalent to those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In such a rotary piston engine, the length of the communication passage 50 is set so that the natural frequency of the air column in the communication passage 50 is one time the suction rotation speed per unit time of each cylinder at a specific engine speed. By setting the height, the dynamic effect can be enhanced at the specific engine speed as shown in FIG. That is, in the rotary piston engine,
As shown by lines F and G in FIG. 11, the intake port 45 and the auxiliary intake port 46 are sequentially opened and closed with respect to each working chamber 43. Then, as the intake port 45 is opened and closed, an intake pressure wave (line H) that approximates a sine wave is generated near the intake port 45. On the other hand, when the pressure vibration also occurs in the communication passage 50 and the cycle T ₃ of the natural vibration of the air column of the communication passage 50 matches the suction cycle T ₀ ′, the resonance pressure wave (line H) is generated in the communication passage 22. Occurs, which enhances the intake pressure wave (line I) and enhances the dynamic effect.

(Effects of the Invention) As described above, the present invention provides the auxiliary intake port and the intake expansion chamber that communicates only with this auxiliary intake port via the communication passage, in addition to the original intake system for supplying intake air. , By causing pressure oscillation in the communication passage due to pressure fluctuation in the cylinder,
Since the length of the communication passage is set so that the resonance state is obtained within the normal rotation speed range, the dynamic effect of intake air can be enhanced by the resonance in the communication passage, and the charging efficiency can be improved. In particular, since the above-mentioned communication passages and the like are provided separately from the intake system for the intake air supply, there is more freedom in setting than when the original intake system alone has a dynamic effect. It has various excellent effects such that it can be simplified and that the dynamic effect can be synergistically enhanced by the original intake system and the communication passage.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a first embodiment of the present invention, FIG. 2 is a side view of the same, and FIG. 3 is an explanatory view showing a pressure fluctuation state in an intake stroke together with valve opening / closing timing, FIG. 4 and FIG. FIG. 5 is an explanatory view of two kinds of specific examples in which the pressure wave in the communication passage resonates, FIG. 6 is a side view showing the second embodiment, and FIG. 7 is a shutter valve in the second embodiment. FIG. 8 is a view showing an open region, FIG. 8 is a side view showing the third embodiment, FIG. 9 is a view showing open timings and opening periods of auxiliary intake ports in the third embodiment, and FIG. 10 is a fourth embodiment. FIG. 11 is a schematic side view, and FIG. 11 is an explanatory view showing the pressure fluctuation state in the case of the fourth embodiment together with the port opening / closing timing. 1 ... Engine body, 2 ... Cylinder, 4 ... Combustion chamber, 6,45
…… Intake port, 9,46 …… Auxiliary intake port, 21,49 ……
Intake expansion chamber, 22,50 ... Communication passage.

Claims (1)

[Claims] 1. An intake port for supplying intake air to a combustion chamber, an auxiliary intake port opened during an intake stroke, and an intake expansion chamber communicating only with this auxiliary intake port via a communication passage. The passage length of the communication passage is set so that the natural frequency of the air column in the communication passage becomes an integral multiple of the number of suction times of one engine cylinder per unit time at a specific engine speed within the practical rotation speed range. The intake system for the engine, which is characterized by