JPS6296744A - Exhaust gas reflux device for mutlicylidner engine - Google Patents

Abstract

PURPOSE:To aim at improvement in engine output with a small-sized supercharger, by connecting a natural suction passage to partial cylinders and a super charging suction passage to remaining cylinders, respectively, and constituting these passages so as to make more plenty exhaust gas flow back to these partial cylinders than that to the remaining ones. CONSTITUTION:There are provided with a supercharging suction passage 3, which is extended from an outlet pipe 2A of an air cleaner 2 and interconnected to both first and fourth cylinders as branched off in the midway, and natural suction passage 4 which is extended from the outlet pipe 2A and interconnected to both second and third cylinders as branched off in the midway. Also there is provided with an exhaust gas recirculation (EGR) passage 21 which is extended from an exhaust passage 20, branched off at a branch box 21A, and interconnected to surge tanks 3A and 4A formed in the downstream of throttle valves 8a and 8b in these suction passage 3 and 4. And, at the branch box 21, each of EGR valves 24a and 24b is to be installed between outlet chamber 22a and 22b to be interconnected to these tanks 3A and 4A and an inlet chamber in common with these outlet chambers, and these valves 24a and 24b are constituted so as to make an EGR quantity to the surge tank 4A more plenty than that to the surge tank 3A.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for a multi-cylinder engine.
In particular, the present invention relates to an exhaust gas recirculation system for a supercharged multi-cylinder engine that supercharges only some cylinders.

(Prior Art) Conventionally, in order to increase the output of an engine, engines that are supercharged using a turbocharger or a mechanical supercharger have generally been widely put into practical use.

In multi-cylinder engines equipped with a supercharger such as the turbocharger or mechanical supercharger mentioned above, the supercharger is generally installed upstream of the intake manifold to supercharge all cylinders. Ta.

By the way, in a supercharged engine, since it is necessary to lower the compression ratio to prevent knocking, there is a problem that the output performance of the engine decreases and the combustion consumption rate worsens, especially at low load.

Therefore, in order to be able to supercharge only at medium to high loads without supercharging at low loads, for example, Japanese Patent Laid-Open No. 59-20
Publication No. 0014 discloses that an auxiliary intake passage is provided in addition to the main intake passage, a supercharger is interposed in the auxiliary intake passage, and a timing pulp valve that is opened at the end of the intake stroke or the beginning of the compression stroke is installed in the auxiliary intake passage. In addition, an EGR passage is provided to recirculate exhaust gas from the exhaust passage to the auxiliary intake passage.At low loads, intake air is supplied by natural intake from the main intake passage, while at medium to high loads, exhaust gas is recirculated to the auxiliary intake passage. However, an intake system for an engine is described in which a supercharger is driven to supply supercharged intake air from an auxiliary intake passage from the end of the intake stroke to the beginning of the compression stroke.

Furthermore, NO in engine exhaust gas has been conventionally used.

Exhaust gas recirculation systems for multi-cylinder engines have been widely put into practical use in order to reduce the combustion temperature in the cylinders by recirculating part of the exhaust gas into the intake passage during light to medium loads. There is.

(Problems to be Solved by the Invention) Generally, supercharged multi-cylinder engines have the following problems.

Both when a turbocharger is used as the supercharger and when a mechanical supercharger is used, the combustion consumption rate deteriorates because the compression ratio is lowered to prevent knocking.

On the other hand, when a turbocharger is installed, there is a time lag due to the inertia of the turbine when accelerating at low speeds, making it impossible to provide sufficient supercharging at the same time as acceleration, and the output performance is inferior to that of a naturally aspirated system due to the low compression ratio. , the acceleration response will be lacking.

Furthermore, in a region where exhaust gas for one or more cylinders is bypassed from the wastegate during high-speed operation, high exhaust pressure is applied to the golden cylinder to bypass it, resulting in an increase in exhaust loss.

In addition, when installing a mechanical supercharger, unless the supercharger is operated intermittently using a clutch mechanism to drive the supercharger only during medium to high loads, the fuel consumption rate will significantly deteriorate. In this case, a torque shock occurs when the clutch mechanism is connected, and the clutch mechanism also becomes large, which is disadvantageous in terms of installation in a car.Mechanical superchargers are generally large and disadvantageous in terms of installation.

In conventional multi-cylinder engines with a supercharger, all cylinders were supercharged, so it was difficult to eliminate the disadvantages of installing a supercharger as mentioned above, and the supercharger also became larger. However, there were problems such as a disadvantage in terms of mountability, a worsening of the combustion consumption rate, and a decrease in acceleration response.

By the way, in a previous application, the applicant of the present application separately provided natural intake passages communicating with some cylinders and supercharging intake passages communicating with the remaining cylinders in a multi-cylinder engine,
An intake system for a multi-cylinder engine has been proposed in which a supercharger is interposed in the supercharged intake passage to supply supercharged intake air only to the remaining cylinders.

In a multi-cylinder engine equipped with the above-mentioned intake system, the compression ratio of the supercharged cylinder must be set lower than that of the naturally aspirated cylinder to prevent knocking in the supercharged cylinder. When installing a recirculation device, if exhaust gas is recirculated uniformly under the same conditions to naturally aspirated cylinders and supercharged cylinders, the required exhaust gas recirculation amount will generally increase as the compression ratio increases. In the case of naturally aspirated cylinders, exhaust gas is supplied in excess of the required exhaust gas recirculation amount, resulting in a decrease in combustion performance and output, while in the case of naturally aspirated cylinders, exhaust gas is supplied in excess of the required exhaust gas recirculation amount, resulting in NOx emissions. It becomes difficult to lower the level sufficiently.

In addition, the engine intake system described in the above publication has a complicated structure such as the provision of an auxiliary intake passage and an auxiliary intake port, but it is difficult to open the main intake valve and the auxiliary intake valve. During this period, air is taken only from the auxiliary intake port, for example, so the amount of intake from the main intake boat does not increase much at the beginning of the intake stroke, which is not very advantageous in terms of cost effectiveness.

(Means for Solving the Problems) The exhaust gas recirculation device for a multi-cylinder engine according to the present invention has a natural intake passage that communicates with some of the cylinders and a naturally intake passage that communicates with the remaining cylinders in the multi-cylinder engine. A supercharging intake passage independent of the passage is provided, a supercharger is interposed in the supercharging intake passage, and exhaust gas is supplied to the communicating cylinder of the natural intake passage and the communicating cylinder of the supercharging intake passage. The compression ratio of the remaining cylinders is set to be lower than the compression ratio of some of the cylinders. The exhaust gas flow rate to each cylinder is increased.

(Function) In the exhaust gas recirculation system for a multi-cylinder engine according to the present invention, as described above, natural intake air (intake air that is not supercharged) is supplied to some cylinders via the natural intake passage, and the remaining cylinders are supplied with natural intake air (intake air that is not supercharged). Supercharged intake air is supplied to the engine through a supercharged intake passage having a supercharger.

Then, the compression ratio of the remaining cylinders connected to the supercharged intake passage is set lower than the compression ratio of some cylinders connected to the natural intake passage, and the exhaust gas is transferred to some cylinders and the remaining cylinders by the exhaust gas recirculation passage. According to the compression ratio, more exhaust gas is recirculated to some cylinders than to the remaining cylinders.

(Effects of the Invention) According to the exhaust gas recirculation device for a multi-cylinder engine according to the present invention, as explained above, in a multi-cylinder engine, natural intake air is supplied to some cylinders, and supercharging is supplied to the remaining cylinders. Since it is configured to supply intake air, it is possible to improve engine output with a relatively small supercharger,
Since the supercharger is small, it is advantageous in terms of installation, and the compression ratio of naturally aspirated cylinders does not have to be lowered, so it is possible to prevent a decrease in fuel consumption.

In other words, by supercharging only some cylinders, it is possible to achieve intermediate characteristics between supercharging all cylinders and naturally aspirating all cylinders, resulting in a relatively small size, efficiency, and durability. With a superior supercharger, it is possible to have both the characteristics of supercharging and the characteristics of naturally aspirated air.

Moreover, by setting the compression ratio of the naturally aspirated cylinders higher than that of the supercharged cylinders, and allowing more exhaust gas to recirculate to the naturally aspirated cylinders than to the supercharged cylinders, the By recirculating an appropriate amount of exhaust gas to the feed cylinder, it is possible to reduce No. while preventing a decrease in engine output and deterioration of fuel efficiency.

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

This embodiment is a case where the exhaust gas recirculation device for a multi-cylinder engine of the present invention is applied to a vertical in-line four-cylinder ignition type engine.

As shown in FIGS. 1 and 2, it extends from the outlet pipe 2A of the air cleaner 2 and branches midway into the first cylinder 1a and the fourth cylinder 1.
d, and a natural intake passage 4 that extends from the outlet pipe 2A of the air cleaner 2, branches midway, and communicates with the second cylinder 1b and the third cylinder 1c. A mechanical supercharging m6 consisting of, for example, a radial compressor is interposed in the middle of the intake passage 3, and is interlocked and connected to the crankshaft 19 with a belt 6a. A relief valve 7 is interposed in a bypass passage 3a that communicates with the passage 3 and the natural intake passage 4.

The bypass passage 3a and the relief valve 7 are for bypassing a part of the intake air pressurized by the supercharger 6 from the supercharged intake passage 3 to the natural intake passage 4 when the engine load is low. The opening degree of the relief valve 7 is reduced in accordance with the increase in the first and fourth cylinders 1.
In order to increase the flow rate of supercharged intake air flowing to a and 1d,
An actuator 9 is provided that adjusts the opening degree of the relief valve 7 in response to intake negative pressure downstream of the throttle valve 8b in the second intake passage 4.

The relief valve 7 is controlled by an actuator 9 that receives negative intake pressure in the natural intake passage 4, as shown in FIG.

That is, the relief valve 7 is kept fully open until the engine load reaches a predetermined low load value, and then the opening degree of the relief valve 7 decreases as the engine load increases.
When the throttle valves 8a and 8b are fully open, the relief valve 7
is now fully closed.

Therefore, at low load, a part of the supercharged intake air with high temperature flows from the supercharged intake passage 3 to the natural intake passage 4 and is supplied to the second and third cylinders lb and 1c.
- The combustibility within the IC is improved, and the rise in pressure and temperature of the supercharged intake air in the supercharged intake passage 3 is suppressed.

Reference numeral 18 is a check valve that opens when the pressure of intake air in the supercharged intake passage 3 exceeds a predetermined value, and releases intake air from the supercharged intake passage 3 to the natural intake passage 4.

Furthermore, as shown in FIG. 2, exhaust gas is supplied to a surge tank 4A downstream of the throttle valve 8b of the natural intake passage 4 and a surge tank 3A downstream of the throttle valve 8a of the supercharged intake passage 3. For reflux, an exhaust gas recirculation passage 21 is provided that extends from the exhaust passage 20, branches at a branch box 21A, and connects to a surge tank 3A and a surge tank 4A. A second outlet chamber connected to the surge tank 4A is formed by a first outlet chamber 22a connected to the tank 3A and a second branch reflux passage 21b.
It is divided into an outlet chamber 22b and an inlet chamber 23 connected to the exhaust passage 20, and a first EGR valve 24a is installed on the partition wall between the first outlet chamber 22a and the inlet chamber 23. A second EGR valve 24b is interposed on the wall, and the first EGR valve 24a and the second EGR pulp 2
A diaphragm-type first actuator 25a and a second actuator 25b are provided to open and close the 4b, respectively, and their negative pressure chambers are connected to the surge tank 4A through the negative pressure introduction path 26.
A solenoid-driven control valve 27 is interposed in the middle of the negative pressure introduction passage 26 to control the area of the passage.

As will be described later, since the compression ratio of the naturally aspirated cylinder is set higher than that of the supercharged cylinder, the naturally aspirated passage 4
The first EGR valve 24a and the second
The relationship between the valve lift amount of the EGR pulp 24b and the passage opening area is set as shown in FIG. 4, for example.

In addition, an injector 10 for injecting fuel into a branch intake passage near the intake boat of each cylinder 1a to 1d is provided, and a surge tank 3A of the supercharging intake passage 3 and a natural intake passage 4 are provided.
The surge tank 4B is provided with pressure sensors 5a and 5b, respectively, and the cylinder block of the engine E is provided with a knock sensor 11 that detects engine vibration. The detection signals from 12 are sent to the control unit 1, respectively.
3, and the control unit 13 outputs operation signals to each of the injectors 10, igniters 14, and control valves 27, respectively.

Furthermore, the first and fourth cylinders 1a and 1 to which supercharged intake air is supplied
For d, the second and third cylinders l are supplied with naturally aspirated air.
b. Since it is necessary to delay the ignition timing compared to the IC, the first spark plug receives the output from the igniter 14 and outputs it to the spark plug of the first cylinder 1a and the spark plug of the fourth cylinder 1d.
A second distributor 1 receives the output from the distributor 15a and the igniter 14 and outputs the output to the spark plug of the second cylinder lb and the spark plug of the third cylinder IC, respectively.
5b is provided.

Here, the ignition order of the four-cylinder engine E is the first cylinder 1a, the third cylinder 1c, the fourth cylinder 1d, and the second cylinder 1b. Supercharged intake air is supplied to the first cylinder 1a and the fourth cylinder 1d which are not adjacent in the direction.

That is, since the output of the supercharged cylinders (first and fourth cylinders 1a and 1d) is large, the torque is increased by alternately igniting the supercharged cylinders and naturally aspirated cylinders (second and third cylinders lb and IC). In order to suppress the fluctuations as much as possible, and to avoid concentration of heat load, the supercharged cylinder should be Make sure they are not adjacent to each other.

Furthermore, for naturally aspirated cylinders, the compression ratio is, for example, 9 to 10.
The compression ratio for supercharged cylinders is set to about 7 to 8, for example, to prevent non-knocking, and the ignition timing is set somewhat later in supercharged cylinders than in naturally aspirated cylinders to prevent knocking. Ru.

In the above configuration, the fuel injection amount to the first cylinder 1a and the fourth cylinder 1d is set by the control unit 13 based on the intake negative pressure detected by the pressure sensor 5a and the engine speed, The amount of fuel injected into the third cylinder 1c is set by the control unit 13 based on the intake negative pressure detected by the pressure sensor 5b and the engine speed.

When the engine E is running, the supercharger 6 is driven by the power from the crankshaft, so the intake air flowing into the supercharging intake passage 3 is approximately 1.5 to 2.0 kg/crA in the supercharger 6.
The supercharged intake air is pressurized to approximately G and is taken into the first and fourth cylinders 1a and 1d, while the natural intake air from the natural intake passage 4 is taken into the second and third cylinders lb and IC.

When the engine load is small, the intake negative pressure on the downstream side of the slow/torque valve 8b in the natural intake passage 4 is large, so the relief valve 7 is opened by the actuator 9 in response to the intake negative pressure as explained based on FIG. Since the supercharged intake air on the downstream side of the supercharger 6 is bypassed to the natural intake passage 4 via the bypass passage 3a, the rise in pressure and temperature between the supercharger 6 and the throttle valve 8a is suppressed, and the supercharging Aircraft 6 will be protected.

Next, exhaust gas recirculation will be explained.

First, exhaust gas recirculation is performed when the engine load is light to medium load in a predetermined operating state, and the ratio of exhaust gas to fresh air during this exhaust gas recirculation is stored in advance in the memory of the control unit 13 in the form of a map or the like. The control valve 27 is controlled by the control unit 13 so that a predetermined exhaust gas recirculation ratio is achieved based on the detection signals from the rotation speed sensor 12 and the pressure sensor 5b, and the opening degree and surge of the control valve 27 are The first and second EGR valves 2 depending on the intake negative pressure in the tank 4A.
4a and 24b are opened, and exhaust gas is recirculated to both surge tanks 3A and 4A via the exhaust gas recirculation passage 21.

At this time, the passage opening areas of both EGR valves 24a and 24b are set as shown in FIG. It will be higher than the exhaust gas flow rate.

In other words, since an appropriate amount of exhaust gas is recirculated to both the naturally aspirated cylinder and the supercharged cylinder according to the respective compression ratios, No. is reduced without deteriorating the fuel efficiency and output.

Next, a part of the above embodiment may be modified as follows.

First modification: As shown in FIG. 5, an outlet chamber 32 communicating with the branch reflux passage 21a and the branch reflux passage 21b and an inlet chamber 33 communicating with the exhaust passage 20 are provided in the branch box 31A, An EGR valve 34 is interposed in the partition wall between the outlet chamber 32 and the inlet chamber 33, and the negative pressure chamber of the actuator 35 of the EGR pulp 34 is connected to the surge tank 4A via the negative pressure introduction path 26, and the negative pressure is A control valve 27 is interposed in the middle of the introduction path 26.

The branch reflux passage 21b has a larger passage area than the branch reflux passage 21a.

Therefore, during exhaust gas recirculation, the flow rate of exhaust gas to the surge tank 4A is greater than the flow rate of exhaust gas to the surge tank 3A.

Second modification: Instead of the injector 10, a carburetor is provided in the supercharging intake passage 3 and the natural intake passage 4, respectively.

Third modification: A turbocharger is provided in place of the supercharger 6. That is, a turbine is provided at the confluence of the exhaust gas passages from the supercharged cylinders, and a compressor is provided in the supercharged intake passage 3.

It goes without saying that the present invention can be applied to not only 4-cylinder engines but also 5- or 6-cylinder engines.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram (plan view) of an in-line four-cylinder engine and its control system, and FIG.
The figure is a diagram showing the overall configuration of the same as above (front view), Figure 3 is a diagram showing the opening degree of the relief valve, and Figure 4 is a diagram showing the relationship between the rift I of the 1st and 22nd GR pulps and the passage opening area. , 5th
The figure is a diagram corresponding to FIG. 2 of a modified example. E...Engine, la~1d...Cylinder, 3...Supercharged intake passage, 4...Natural intake passage, 6...Supercharger, 8a
・8b...Throttle valve, 21...Exhaust gas recirculation passage,
21a, 21b... Branch reflux passage. Patent applicant: Mazda Motor Corporation Agent: Toshio Okamura

Claims (1)

[Claims] (1) In a multi-cylinder engine, a naturally aspirated passage that communicates with some of the cylinders, a supercharged intake passage that communicates with the remaining cylinders and is independent of the naturally aspirated passage, and a supercharged intake passage that is interposed in the supercharged intake passage. a supercharger, and an exhaust gas recirculation passage that supplies exhaust gas to the cylinders with which the natural intake passage communicates and the cylinders with which the supercharged intake passage communicates; The compression ratio of the cylinder is set low, and the exhaust gas recirculation passage is configured such that the flow rate of exhaust gas to some of the cylinders is larger than the flow rate of exhaust gas to the remaining cylinders. Engine exhaust gas recirculation device.