JPH08254126A - Automotive engine - Google Patents

Abstract

PURPOSE: To improve low speed torque and also sufficiently secure high speed torque, while intake valves and exhaust valves are subjected to fixing timing. CONSTITUTION: While the closing timing of the intake valves 5, 6 of an engine is regarded as low speed type timing to improve filling efficiency in a low speed range, the opening timing of exhaust valves 7, 8 is regarded as high speed type timing suitable for accelerating exhaust in a high speed range so that a period from exhaust valve opening timing to an exhaust bottom dead center is increased more than 10 degrees at an crank angle, larger than a period from an intake bottom dead center to intake valve closing timing. Further, turbulent flow strength raising means provided with a first intake port 3 for generating eddy current and a second intake port 4 closed in the low speed range is arranged in an engine and hereby, a combustion period is shortened in the low speed range, and exhaust energy can be sufficiently applied to a piston before the exhaust valves 7, 8 as the high speed type timing are opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile engine equipped with intake and exhaust valves that are opened and closed at fixed timings.

[0002]

2. Description of the Related Art Conventionally, in an automobile engine including an engine body having a combustion chamber, an intake valve, an exhaust valve, etc., an intake system and an exhaust system connected to the engine body, Various improvements have been made to the structure of the intake / exhaust system and the shape of the combustion chamber in order to improve the combustibility of the air-fuel mixture or increase the torque. For example, Japanese Patent Laid-Open No. 5-1
The intake device disclosed in Japanese Patent Publication No. 06451 includes a P port for swirl generation and an S port that is closed when the load is low. When the S port is closed, intake air from the P port enters the combustion chamber. Swirl is generated to accelerate the ignition and combustion of the air-fuel mixture.

[0003]

By the way, in the conventional automobile engine in which the intake valve and the exhaust valve are opened and closed at a fixed timing, the exhaust BDC (exhaust bottom dead center) from the exhaust valve opening timing. ) Period and intake BDC
The period from (intake bottom dead center) to the intake valve closing timing is set to be approximately the same. That is, in order to increase the low speed torque of the engine, the intake valve and the exhaust valve are set to the low speed type timing, and at this low speed type timing, the period from the exhaust valve opening timing to the exhaust BDC and the intake BDC are set.
The period from to the intake valve closing timing is shortened to the same extent.
Further, when trying to increase the high speed torque of the engine, the intake valve and the exhaust valve are set to high speed type timing, and at this high speed type timing, the period from the exhaust valve opening timing to the exhaust BDC and the intake BDC to the intake valve are set. The period until the closing time is extended to the same extent.

However, with such setting of the opening / closing timing of the intake / exhaust valve, it is difficult to increase the torque in the low speed region and the high speed region.

Therefore, one of the intake valve and the exhaust valve is a low speed type, and the other is a high speed type. For example, the intake valve is opened and closed at a low speed type in order to increase the low speed torque, and the exhaust valve is set to supplement the high speed torque. Although it is possible to set the high-speed type opening / closing timing, even in this case, in the low speed range, since the exhaust valve is opened quickly, a large amount of combustion energy is released to the exhaust side, so that the effect of increasing the low speed torque is impaired. The problem arises.

[0006] Incidentally, there is a configuration in which the opening / closing timing of the intake / exhaust valve is changed according to the operating state to increase the torque in each rotational speed range.
The mechanism and control for changing the opening / closing timing becomes complicated.

In view of the above circumstances, it is an object of the present invention to provide an automobile engine capable of increasing low-speed torque and sufficiently securing high-speed torque while fixing the intake valve and the exhaust valve at fixed timing. And

[0008]

According to a first aspect of the present invention, there is provided rapid combustion means for rapidly burning the air-fuel mixture in the combustion chamber at least in the low speed range of the engine to shorten the combustion period, and closing the intake valve. The timing is low-speed timing that enhances filling efficiency in the low-speed range, while the exhaust valve opening timing is high-speed timing suitable for promoting exhaust in the high-speed range, and the period from the exhaust valve opening timing to the exhaust bottom dead center is intake The crank angle is increased by 10 deg or more than the period from the bottom dead center to the intake valve closing timing.

According to a second aspect of the present invention, in the engine according to the first aspect, turbulent flow intensity increasing means for increasing the intensity of the turbulent flow in the combustion chamber due to introduction of intake air into the combustion chamber is provided as the rapid combustion means. The turbulent flow intensity increasing means is operated at least in the low speed range of the engine.

According to a third aspect of the present invention, in the engine according to the second aspect, the turbulent flow intensity increasing means sets the average turbulent flow intensity in the combustion chamber within a range of 1.5 to 2.5 m / sec. It was done like this.

According to a fourth aspect of the present invention, in the engine according to the second or third aspect, the turbulent flow intensity increasing means has a first intake port for generating a vortex flow and a second intake port closed in a low speed range. It is equipped with and.

According to a fifth aspect of the present invention, in the engine according to the fourth aspect, the angle formed by the center line of the vortex formed in the combustion chamber by the intake air flowing from the first intake port and the cylinder center line is determined. The swirl ratio of the vortex is set to about 3 or more while being set in the range of 35 ° to 55 °.

The invention according to claim 6 is the same as claims 1 to 5.
In the engine described in any one of 1, the means for shortening the flame propagation distance in the combustion chamber is provided as the rapid combustion means.

According to a seventh aspect of the invention, in the engine according to the sixth aspect, a plurality of spark plugs are arranged in the combustion chamber as means for shortening the flame propagation distance in the combustion chamber.

[0015]

According to the engine of the first aspect, the intake valve closing timing is set to the low speed type timing, so that the charging efficiency is increased in the low speed range and the low speed torque is increased. on the other hand,
The combustion period is shortened by the rapid combustion means while the exhaust valve is opened at a relatively high speed, and a large amount of combustion energy is prevented from being discharged to the exhaust side, thereby increasing the low speed torque. Is not damaged. In the high speed range, since the exhaust valve is set to the high speed type timing, the exhaust is promoted and the pumping loss during the exhaust is reduced, so that the intake valve is set to the low speed type timing in the high speed range. The decrease in torque is compensated.

In the present invention, when the turbulent flow intensity increasing means is provided as the rapid combustion means as described in claim 2, combustion is promoted by the increase in turbulent flow intensity in the combustion chamber and the combustion period is shortened. It is possible to effectively obtain the effect of ensuring low speed torque while opening the exhaust valve at high speed. In this case, when the average turbulence intensity in the combustion chamber is set in the range of 1.5 to 2.5 m / sec as described in claim 3, the combustion speed can be sufficiently increased within the range that does not impair the ignitability.

According to a fourth aspect of the present invention, the turbulent flow intensity increasing means comprises a first intake port for generating a vortex flow and a second intake port closed in a low speed range.
In the low speed range where the second intake port is closed, the vortex flow is generated to promote combustion and shorten the combustion period.
In this case, when the angle formed by the center line of the vortex and the center line of the cylinder is set within the range of 35 ° to 55 ° and the swirl ratio is set to about 3 or more in this case,
The average turbulence intensity is strengthened and the burning velocity is sufficiently increased.

Further, as described in claim 6, even if the means for shortening the flame propagation distance in the combustion chamber is provided as the rapid combustion means, the combustion period is shortened, and the opening timing of the exhaust valve is set to the high-speed timing. However, the effect of ensuring low-speed torque can be effectively obtained. As a means for shortening the flame propagation distance, for example, by disposing a plurality of spark plugs in the combustion chamber as described in claim 7, the combustion period is sufficiently shortened.

[0019]

An embodiment of the present invention will be described with reference to the drawings.
First, an outline of an automobile engine will be described with reference to FIG. In the figure, reference numeral 1 is an engine body, and a combustion chamber 2 is formed in each cylinder of the engine body. The combustion chamber 2 has first and second intake ports 3 and 4 and a first intake port 3 and 4, which will be described in detail later. The second exhaust ports 5 and 6 are opened, and the intake valves 7 and 8 and the exhaust valves 9 and 10 are installed in these ports 3 to 6.

The engine intake system 20 is provided with an intake manifold 21, which will be described in detail later, and a common intake passage 30 on the upstream side thereof. The common intake passage 30 has an air cleaner 31 and a thermal type in order from the upstream side. An air flow sensor 32 and a throttle valve 33 are arranged. Further, an intake bypass passage 34 that bypasses the throttle valve 33 is formed. The intake bypass passage 34 includes an ISC passage 35 for adjusting the intake air amount during idling and the like, and an air passage 36 for increasing the intake air amount during cold conditions. The ISC passage 35 is duty-controlled to control the air flow rate of the ISC passage 35.
A valve 37 is provided, and the air passage 36 is provided with a temperature sensitive valve 38 that opens when cold.

Further, in the vicinity of the intake port on the downstream side of the intake system 20, injectors 4 for injecting and supplying fuel for each cylinder.
0 is provided, and an on-off valve 41 that opens and closes the second intake port 4 is provided. The on-off valve 41 is operated by a negative pressure responsive actuator 42, and a drive system for the same is provided with a vacuum tank 43 for storing the negative pressure introduced from the surge tank of the intake manifold 21, and between the tank 43 and the actuator 42. Solenoid valve 4 that is arranged in the
4 etc. are provided.

The injector 40 is a so-called AMI (air mixture type injector) which atomizes the fuel by introducing mixing air near the injection port. The injector 40 is provided with a fuel supply system including a fuel supply passage 48 for supplying fuel from a fuel tank 45 via a fuel pump 46 and a filter 47, a return passage 50 in which a pressure regulator 49 is provided, and the like. A mixing air supply system and an evaporated fuel supply system are provided.

The mixing air supply system includes an AMI air supply passage 52 having an air control valve 51. The AMI air supply passage 52 has an upstream side connected to the intake bypass passage 34 and a downstream side branched. Is connected to each injector 40. The air control valve 51 is closed at the time of idling and at the time of high load, and supplies the air to the injector 40 at other times.

The evaporative fuel supply system is a canister 56.
And a purge passage 57 extending from the purge passage 57.
Is equipped with a purge solenoid valve 58. The purge passage 57 is connected to the mixing chamber 55 formed upstream of the branch point of the AMI air supply passage 52. Then, the evaporated fuel generated in the fuel tank or the like and trapped in the canister 56 is supplied to the vicinity of the injection port of each injector 40 via the purge passage 57 when the purge solenoid valve 58 is opened, and the fuel is supplied during the intake stroke. It is supplied with the spray to the combustion chamber 2 of each cylinder.

On the other hand, the exhaust system has an oxygen concentration sensor 6 for detecting the oxygen concentration in the exhaust gas corresponding to the air-fuel ratio of the air-fuel mixture.
0 and a catalyst device 61 are provided.

As various detecting elements for controlling the engine, in addition to the air flow sensor 32 and the oxygen concentration sensor 60, a throttle opening sensor 62 for detecting the opening of the throttle valve, and an idle for detecting the throttle fully closed. A switch 63, an intake air temperature sensor 64 for detecting an intake air temperature, a water temperature sensor 65 for detecting an engine water temperature, a knock sensor 66 for detecting an engine knock, and the like are provided, and a crank angle signal is output to an ignition system distributor 67. There is provided a crank angle sensor 68 that operates and a cylinder discrimination sensor 69 that outputs a cylinder discrimination signal.

The signals from these detection elements are input to a control unit (ECU) 70 for controlling the engine. The control unit 70 controls the fuel injection amount and injection timing from the injector 40, and further, the ISC valve 37, the solenoid valve 44 in the drive system of the on-off valve 41, the air control valve 55, the purge solenoid valve 58, etc. Is also controlled by the control unit 70.

Further, this automobile engine is provided with a rapid combustion means for rapidly burning the air-fuel mixture in the combustion chamber at least in the low speed region to shorten the combustion period. For example, the combustion chamber is constructed by introducing intake air into the combustion chamber. Turbulent flow intensity increasing means for increasing the intensity of the turbulent flow and means for shortening the flame propagation distance in the combustion chamber are provided as the rapid combustion means. Specific examples of such rapid combustion means will be described with reference to FIGS.

FIG. 2 is a schematic plan view of the combustion chamber and the intake / exhaust ports, FIG. 3 is a schematic cross-sectional view of a portion that vertically cuts the combustion chamber and the first intake port and the first exhaust port, and FIG. 4 is a combustion chamber and the second FIG. 6 is a schematic cross-sectional view of a portion that vertically cuts the intake port and the second exhaust port, FIG. 5 is a bottom view of a combustion chamber constituting portion of the cylinder head seen from below, and FIG. 6 is a combustion chamber, a first intake port, and a first intake port. FIG. 3 is a detailed cross-sectional view of a portion that vertically cuts one exhaust port. In these figures, the engine body 1 is provided with a turbulent flow intensity increasing means as one of the rapid combustion means, and this turbulent flow intensity increasing means and the second intake port 3 for generating a vortex flow It has an intake port 4. Furthermore, the flame propagation distance is shortened by using a compact combustion chamber structure, which also shortens the combustion period.

Specifically, in each cylinder of the engine body 1, basically, the first and second intake valves 7 and 8 are provided.
When the engine is opened, the air-fuel mixture is sucked into the combustion chamber 2 through the first and second intake ports 3 and 4, and this air-fuel mixture is transferred to the piston 11
So that the combustion gas is discharged from the first and second exhaust ports 5 and 6 when the first and second exhaust valves 9 and 10 are opened by being ignited and burned by the spark plug 12 after being compressed by. Has become. Then, the first intake port (hereinafter,
The injector 40 is provided in the P port 3 and the second intake port (hereinafter referred to as the S port) 4 or a passage upstream thereof (S side branch passage 23s described later) is provided with the injector 40.
An on-off valve 41 that is controlled to open and close according to the operating state is provided, and when the on-off valve 41 is closed, a strong swirl (vortex flow) is generated in the combustion chamber 2 by the intake air introduced into the combustion chamber 2 from the P port 3. ) Is generated.

In this embodiment, when the on-off valve (hereinafter referred to as TSC valve) 41 as a tumble / swirl control valve is closed, a strong tumble (vertical vortex) and swirl (horizontal vortex) are combined. The port arrangement, the port shape, etc. are set so that such a spiral oblique swirl is generated in the combustion chamber 2.

More specifically, the P port 3 and the S port 4 have straight portions 3a, 4a extending substantially linearly in the upstream portion in the intake flow direction, and downward in the vicinity of the downstream ends of the straight portions 3a, 4a. It is constituted by curved portions 3b and 4b which are curved and reach the respective valve seats 13 and 14 (see FIGS. 3 and 4). The extension lines of the port center lines Lp1 and Ls1 of the straight portions 3a and 4a of the P port 3 and the S port 4 are
The valve end portion 7 located on the center side of the combustion chamber 2 at the time of maximum lift of the valve seats 13 and 14 and the first and second intake valves 7 and 8.
It is set so as to pass between a and 8a. As a result, the flow resistance of the intake air supplied from the P, S ports 3 and 4 to the combustion chamber 2 is reduced. The above port center line Lp
1, the extension lines of Ls1 are the valve seats 13 and 14 and the valve end portion 7
It is optimal to set so as to pass through the centers of a and 8a.

The combustion chamber 2 is a pentroof lens type combustion chamber in which the lower surface of the cylinder head 1a is in a pentroof shape, and the valve grip angle θ between the intake valves 7, 8 and the exhaust valves 9, 10 is 30. It is narrowed to about 0 ° and is driven by a DOHC direct drive type valve mechanism (not shown). Further, the angle formed between the valve center line L1 of the first intake valve 7 and the throat center line Lp1 of the P port 3 (throat offset angle α1) is relatively large, and
Angle formed by the valve center line L2 of the intake valve 8 and the throat center line Ls1 of the S port 4 (throat offset angle α2)
Is set relatively small, for example, α1 = 30 °,
α2 = 12 °. In this way, when the intake is performed only from the P port 3, the vortex S having an inclination angle (angle with the cylinder center line) γ of 35 ° to 55 ° is generated. Further, the S port 4 is adapted to generate a tumble T in the combustion chamber 2.

The intake valves 7 and 8 are respectively
The valve shaft portion 7b, 8b and the umbrella portion 7c, 8c, and the umbrella portion 7
The lower surfaces of c and 8c are arranged so as to be parallel to the ceiling surface of the combustion chamber 2. The valve umbrella angle β1 of the first intake valve 7 (the angle between the lower surface and the upper surface of the umbrella portion) β1 is the valve umbrella angle β of the second intake valve 8.
It is set larger than 2. As a result, the flow path between the first intake valve 7 and the throat portion of the P port 3 at the time of valve lift becomes narrower than the flow path between the second intake valve 8 and the throat portion of the S port 4, and thus , The intake flow velocity is increased on the P port 3 side, and the flow rate is secured on the S port 4 side.

Further, a port edge 15 is formed in the lower portion of the outlet of the P port 3, and a squish area 16 is formed around the first intake valve 7 in the combustion chamber 2, whereby the exhaust gas from the P port 3 is formed. The flow velocity of air blown to the valve side is increased.

In this way, the turbulent flow intensity increasing means is constructed. According to this turbulent flow intensity increasing means, the P port 3
The combustion speed is increased by, for example, obtaining a strong vortex flow that combines tumble and swirl by the intake air from.

That is, as shown in FIG. 8, the swirl is
The turbulence intensity from the intake to the first half of the compression stroke is great,
Although the effect of homogenizing the air-fuel mixture is large, the turbulence strength in the latter half of the compression stroke is small, and conversely, the tumble has a small turbulence strength in the first half of the compression stroke but a large turbulence strength in the latter half of the compression stroke.
Further, in the case of the above intake port structure, the advantages of both swirl and tumble are obtained, and the average turbulence intensity from the intake stroke to the compression stroke is increased. FIG. 7 shows a case where the swirl ratio Sr is 3.3 and a case where the swirl ratio Sr is 4.2.
The relationship between the swirl inclination angle (angle formed by the swirl center line and the cylinder center line) γ and the average turbulence intensity R is shown.
As shown in this figure, by setting the swirl ratio Sr to about 3 or more and the swirl inclination angle γ in the range of 35 ° to 55 °, particularly preferably 45 °, the average turbulence intensity is significantly increased. , The homogenization of the air-fuel mixture and the burning rate are improved. The average turbulence intensity is preferably set to 1.5 to 2.5 m / s in order to increase the combustion speed within a range that does not impair the ignitability.

Here, the definition and method of obtaining the swirl ratio will be described. The swirl ratio is generally defined as a value obtained by dividing the number of revolutions of the lateral vortex of the air-fuel mixture (intake air) in the cylinder by the engine speed.

The number of swirling lateral vortices of the air-fuel mixture is set to a position F ₂ below the cylinder head lower surface F ₁ by a distance of 1.75 D in an engine having a bore diameter D as shown in FIG. The impulse swirl meter 80 is arranged, the torque acting on the impulse swirl meter 80 (impulse swirl meter torque) is detected, and it is calculated by a well-known method based on this impulse swirl meter torque. In FIG. 7, F ₃ represents the top surface of the piston 11 at the bottom dead center position.

The impulse swirl meter torque is measured by the following procedure. That is, by arranging the impulse swirl meter 80 at the position of F ₂ and reproducing the energy of the swirl acting on the piston top surface by the impulse swirl meter 80, how much revolving energy is generated in the vicinity of the piston top surface under normal conditions. Determine if it is present. The impulse swirl meter 80 is equipped with a large number of honeycombs.
When a swirl acts on the honeycomb, a force in the swirl flow direction acts on each honeycomb, and the impulse swirl meter torque G acting on the whole is calculated by integrating the forces applied to each honeycomb.

More specifically, assuming that the air-fuel mixture is being sucked into the combustion chamber 2 during the period from the opening of the intake valve to the bottom dead center, the air-fuel mixture is kept in the inner peripheral surface of the combustion chamber 2 during this period. It makes a turn along and the turning speed becomes maximum at the bottom dead center position.
Therefore, the swirl ratio can be obtained by integrating the angular momentum of each crank from the start of opening of the intake valve to the bottom dead center. Based on such knowledge, in this example, the swirl ratio Sr is calculated by the following equations (1) and (2).

[0042]

[Equation 1] Sr = ηv · {D · S · ∫ (cf · Nr · dα)} / {n · d ² · (∫cf · dα) ² } ... (1) Nr = 8 · G / (M・ D ・ V ₀ ) (2) where Sr is the swirl ratio and ηv is the volumetric efficiency (ηv =
1), D is the bore diameter, S is the stroke, n is the number of intake valves, d
Is the throat diameter, cf is the flow coefficient for each valve lift,
Nr is a dimensionless rig swirl value for each valve lift,
α is the crank angle, G is the impulse swirl meter torque, M is the mass of air filled in the cylinder during the intake stroke, and V ₀ is the speed head.

The above equation (2) is derived by the following procedure.

[0044]

[Number 2] G = I · ωr ...... (3 ) I = M · D 2/8 ...... (4) (4) and (3) an assignment ^{G = M · D 2 · ωr} / 8 ...... (5 ) From (5) D ・ ωr = 8 ・ G / (M ・ D) …… (6) By the way, Nr = D ・ ωr / V ₀ …… (7) (6) is substituted into (7) Nr = 8 ・G / (M · D · V ₀ ), where I is the moment of inertia of the air in the cylinder at the end of the intake stroke (piston bottom dead center), and ωr is the rig swirl value.

Further, the combustion chamber 2 shown in FIGS.
Has a cylinder bore diameter smaller than that of the piston stroke, has the above-described pentroof lens type combustion chamber, and has a squish area 16,
By forming 17 and 18, a compact combustion chamber that shortens the flame propagation distance from the spark plug 12 located at the center of the combustion chamber to the periphery of the combustion chamber as much as possible is formed.

By the way, as a preferred example of basic engine specifications, a 4-cycle 4-cylinder DOHC engine has a displacement of about 1500 cc, a bore diameter of about 75 mm, a stroke of about 84 mm, and a compression ratio of thermal efficiency. A higher value is preferable, but it is set to 9.4 in consideration of improvement of knocking limit and emission.

The intake valves 7 and 8 and the exhaust valves 9 and 1
The opening / closing timing of 0 is set as shown by the solid line in FIG. That is, the exhaust valve is the exhaust BDC (bottom dead center)
The valve starts to open earlier and closes near TDC (top dead center), and the intake valve starts to open near TDC and closes after intake BDC. Is a relatively short time), and the low-speed timing is suitable for increasing the intake amount in the low speed range (suppressing the blowback of intake air). On the other hand, the exhaust valve opens at timing E
O is a relatively early time (a time until the BDC is relatively long), which is a high-speed timing suitable for promoting exhaust in the high-speed range. The period Te from the exhaust valve opening timing EO to the exhaust BDC is longer than the period Ti from the intake BDC to the intake valve closing timing IC by 10 degCA or more. For example, when the exhaust valve opening timing EO is BBDC50degCA,
The same closing time is ATDC 0degCA, and the intake valve opening time is BTDC 10deg.
CA, IC at the same closing time is ABDC33degCA. These periods are defined in terms of the maximum ramp height of the cam.

The broken line in FIG. 10 shows an example of the opening and closing timings of the intake valve and the exhaust valve in the conventional engine.
The period up to DC and the period from intake BDC to the intake valve closing timing are approximately the same (the difference between the two is 5 degCA or less).

11 to 13 show a specific structure of the intake manifold 21. The intake manifold 21 shown in these figures does not have a switching mechanism because the dynamic effect (inertial effect) of intake air can be switched between a state in which it is synchronized in the low speed range and a state in which it is synchronized in the high speed range. (Ineffective) Compared to the case of (no effect), the intake charging efficiency is increased in the low speed region and the high speed region, and by improving the torque between these regions, the torque in the low speed region contributing to the expansion of the lean burn region is improved. Equipped with a resonance chamber.

The intake manifold 21 has an upper half 21a.
And a lower half portion 21b, and the lower surface of the upper half portion 21a and the upper surface of the lower half portion 21b are joined and integrated. A surge tank 22 as an intake passage collecting portion extending in the cylinder row direction is formed in the upper half portion 21a.
In addition, an independent intake passage 23 for each cylinder that communicates with the surge tank 22 is formed in a range extending from the front surface side (the left side in FIGS. 11 and 12) of the upper half portion 21a to the front surface side and the lower surface side of the lower half portion 21b. In the example shown in FIG. 13, the first to fourth four independent intake passages 2 should be applied to a four-cylinder engine.
3 are formed.

That is, the upper half portion 21a is formed with the upstream portion 23a of each independent intake passage 23, which is connected to the surge tank 22, and the lower half portion 21b is provided downstream of each independent intake passage 23. A side portion 23b is formed, and its downstream end opens to a mounting flange 24 connected to one side portion of the cylinder head of the engine body 1. The surge tank 22 is connected to a throttle body (not shown) on one end side of the upper half portion 21a, and the air passing through the throttle body is introduced into the surge tank 22 and burns through the independent intake passages 23. It is supplied to the room.

In the downstream side portion of each of the independent intake passages 23, a P-side branch passage 23p is connected to the P-port of each cylinder.
And the S-side branch passage 23s connected to the S port, the partition 2
It is branched at 5. Further, each S side branch passage 2
The TSC valve 41 is provided at 3s. Each TSC valve 41 is connected to a valve shaft 41a that penetrates each branch passage in the cylinder column direction so as to be integrally opened and closed. An actuator 42 is connected to the end of the valve shaft 41a, and each TSC valve 41 is opened and closed by the operation of the actuator 42.

A resonance chamber 26 extending between the surge tank 22 and the independent intake passage 23 below the surge tank 22 in the cylinder row direction and communicating with the surge tank 22.
Is provided, and a vertical wall 27 is provided at the side of the resonance chamber 26 on the engine body side. Then, the surge tank 22, the independent intake passage 23, and the vertical wall 27
The resonance chamber 26 is surrounded by and.

That is, the resonance chamber 26
Is formed by covering a concave portion provided on the upper surface of the lower half portion 21b of the intake manifold 21 and opening upward with the upper half portion 21a. The vertical wall 27 is divided into an upper portion 27a and a lower portion 27b as the intake manifold 21 is divided into an upper half portion 21a and a lower half portion 21b. The surge tank 22 is formed to have a relatively small capacity, whereas the resonance chamber 26 is formed to have a large capacity.

A communication passage 28 extending in the cylinder row direction is formed on the rear surface side of the upper half portion 21a. One end 28a of the communication passage 28 is in the resonance chamber 26 and the other end 2 is formed.
8b are opened to the surge tank 22 respectively. Further, the upper half portion 21a is provided with a part of a passage 52 of a mixing air supply system for the injector 40, which will be described later in detail.

In such an intake manifold 21, the dynamic effect of intake is synchronized on the low speed side (for example, about 2000 rpm) when the TSC valve 41 is closed, and relatively high speed when the TSC valve 41 is open. The length, passage area, etc. of the independent intake passage 23 are set so that the dynamic effect of intake air is synchronized on the side (for example, 3500 to 4000 rpm).

Further, only by doing so, the torque is increased on the low speed side and the relatively high speed side as shown by the broken line in FIG. 14, and a valley of the torque is generated at the intermediate portion between them, but as described above, the surge occurs. The tank 22 has a relatively small capacity, and the resonance chamber 26 having a large capacity is connected to the tank 22 to increase the intake charge amount in the intermediate portion by the resonance action of the resonance chamber 26, as shown by the solid line in FIG. The torque changes smoothly. The alternate long and short dash line in the figure shows the torque change when there is no dynamic effect of intake air.

According to the vehicle engine of the present embodiment as described above, since the intake valves 7 and 8 are of the low speed type in which the closing timing is relatively early, the blowback of the intake air is prevented in the low speed region and the charging efficiency is improved. The low speed torque is increased. on the other hand,
Although the exhaust valves 9 and 10 are high-speed type timings in which the opening timing is relatively early, the action of increasing the low-speed torque is maintained by providing the rapid combustion means for shortening the combustion period. That is, the turbulent flow intensity increasing means having the structure as shown in FIGS. 2 to 6 produces an oblique swirl in the low speed range where the TSC valve 41 is closed to accelerate the combustion speed, and the more compact combustion chamber structure is provided. Since the flame propagation distance is shortened and the combustion period is shortened by these effects, even if the opening timing of the exhaust valves 9 and 10 is advanced, the combustion energy is sufficiently given to the piston before the exhaust valve opens, and the exhaust gas is exhausted. A large amount of combustion energy is not released to the side, and the action of increasing the low speed torque is not impaired.

In the high speed range, since the exhaust valves 9 and 10 are set to the high speed type timing, the exhaust is promoted and the pumping loss during the exhaust is reduced, so that the intake valves 7 and 8 are set to the low speed type timing. The torque decrease in the high speed range due to the above is compensated.

In the above embodiment, the turbulent flow intensity increasing means having the P port 3 for eddy current generation and the S port 4 closed in the low speed region as the rapid combustion means, and the flame propagation distance due to the compact combustion chamber structure. However, it is also possible to provide only one of the turbulent flow intensity increasing means and the flame propagation distance shortening means.

As means for shortening the flame propagation distance, in addition to the compact combustion chamber structure as shown in the above embodiment, for example, as shown in FIG. 15, spark plugs 12A are provided at a plurality of places in the combustion chamber 2. , 12B, 12C, it is possible to employ a structure in which the flame propagation distance from each spark plug is shortened and rapid combustion is performed.

Besides, the structure of each part of the automobile engine may be variously modified without departing from the gist of the present invention.

[0063]

As described above, according to the engine of the present invention, the intake valve is set to the low speed type timing in which the closing timing is early, so that the filling efficiency in the low speed range is improved and the exhaust valve is set to the high speed type timing. By reducing the combustion period by the combustion means, it is possible to suppress the release of combustion energy to the exhaust side and effectively increase the low-speed torque, and by making the exhaust valve a high-speed type timing, the intake valve is a low-speed type. It is possible to compensate for the torque decrease in the high speed range due to the timing. Therefore, it is possible to increase the low-speed torque and sufficiently secure the high-speed torque while the intake / exhaust valve has a fixed timing.

In the present invention, if the turbulence intensity increasing means is used as the rapid combustion means to increase the turbulence intensity in the combustion chamber, the combustion period can be effectively shortened, and especially the average turbulence in the combustion chamber can be reduced. Strength of 1.5-2.5m / sec
By setting the above range, the combustion period can be sufficiently shortened within the range that does not impair the ignitability, and the above effect can be enhanced.
More specifically, if a swirl in an oblique direction with an angle of 35 ° to 55 ° is generated in the combustion chamber and the swirl ratio is set to about 3 or more, the average turbulence intensity can be sufficiently increased. Thus, the above effect can be enhanced.

The above effect can also be obtained by providing a means for shortening the flame propagation distance in the combustion chamber as the rapid combustion means, and disposing a plurality of spark plugs in the combustion chamber, for example.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an engine of the present invention.

FIG. 2 is a schematic plan view showing a combustion chamber structure.

FIG. 3 is a schematic sectional view of a first intake port side.

FIG. 4 is a schematic sectional view of a second intake port side.

FIG. 5 is a bottom view of the combustion chamber constituting portion of the cylinder head as viewed from below.

FIG. 6 is a detailed cross-sectional view of a portion that vertically cuts the combustion chamber and the first intake port and the first exhaust port.

FIG. 7 is a characteristic diagram of average turbulence intensity.

FIG. 8 is a diagram showing a comparison between swirl and tumble.

FIG. 9 is an explanatory diagram showing a measuring means and a measuring method for swirl.

FIG. 10 is a diagram showing valve timing.

FIG. 11 is a sectional view of an intake manifold portion.

FIG. 12 is a sectional view of another position of the intake manifold portion.

13 is a view taken along line XIII-XIII in FIG.

FIG. 14 is a diagram showing characteristics of engine torque.

FIG. 15 is a schematic plan view showing another example of the rapid combustion means.

[Explanation of symbols]

 1 Engine Body 2 Combustion Chamber 3,4 Intake Port 5,6 Exhaust Port 7,8 Intake Valve 9,10 Exhaust Valve 12 Spark Plug 16,17,18 Squish Area 41 Open / Close Valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 41/02 301 F02D 41/02 301G 43/00 301 43/00 301Z 301U F02M 69/00 360 F02M 69/00 360A 360C (72) Inventor Yasuyoshi Hori, 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor, Futoshi Nishioka 3-1-1 Shinchu, Fuchu-cho, Aki-gun, Hiroshima Prefecture (Mazda Co., Ltd. ( 72) Inventor Tetsushi Hosogai, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Kenji Oka, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture (72) Inventor, Hideshi Terao No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor Misao Fujimoto No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture No. 1 Mazda Co., Ltd. (72) Inventor Masaki Harada No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (7)

[Claims] 1. A low-speed type timing device which comprises a rapid combustion means for rapidly combusting an air-fuel mixture in a combustion chamber at least in a low speed region of an engine to shorten a combustion period, and which closes an intake valve in a low speed region to improve filling efficiency. On the other hand, the exhaust valve opening timing is set to a high-speed timing suitable for promoting exhaust in the high speed range, and the period from the exhaust valve opening timing to the exhaust bottom dead center is set to be shorter than the period from the intake bottom dead center to the intake valve closing timing. Crank angle is 10
An automobile engine characterized by being made larger than deg. 2. The rapid combustion means includes turbulent flow intensity increasing means for increasing the intensity of turbulent flow in the combustion chamber by introducing intake air into the combustion chamber, and operates the turbulent flow intensity increasing means at least in a low speed region of the engine. The vehicle engine according to claim 1, characterized in that. 3. The engine for an automobile according to claim 2, wherein the turbulent flow intensity increasing means sets an average turbulent flow intensity in the combustion chamber within a range of 1.5 to 2.5 m / sec. . 4. The turbulent flow intensity increasing means is provided with a first intake port for generating a vortex flow and a second intake port closed in a low speed range. The automobile engine described in. 5. The angle between the center line of the vortex formed in the combustion chamber by the intake air flowing from the first intake port and the cylinder center line is set within the range of 35 ° to 55 °, and the vortex flow The vehicle engine according to claim 4, wherein the swirl ratio is set to about 3 or more. 6. The automobile engine according to claim 1, further comprising means for shortening a flame propagation distance in the combustion chamber as the rapid combustion means. 7. The vehicle engine according to claim 6, wherein a plurality of spark plugs are provided in the combustion chamber as means for reducing the flame propagation distance in the combustion chamber.