JP7385353B2 - internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine having a unique fuel control structure during warm-up operation.

In internal combustion engines, harmful substances emitted from exhaust gas include gas components such as NOx and solid PM (particulate matter). Regarding PM, there is a transition from mass regulation to quantity regulation (PN).

Looking at engine types, diesel engines emit PM even after warm-up, so they must be equipped with a filter device such as a DPF as standard, but gasoline engines emit PM even after warm-up. If complete combustion occurs in the combustion process, the amount of PM is small.

However, even in a gasoline engine, when the engine is operated at a low temperature such as during warm-up during a cold start, PM may be generated due to insufficient vaporization (refining) of the fuel. Therefore, although GPF has been developed as a PM countermeasure for gasoline engines, a more fundamental issue is the need for technology to suppress the amount of PM generated.

Therefore, we will consider that the main cause of PM generation in gasoline engines is insufficient vaporization of the fuel, as mentioned above. Therefore, if fuel vaporization can be promoted even when the engine temperature is low, PM generation can be significantly reduced. It can be said that it becomes possible to clear the PN without using GPF.

As a technique for promoting vaporization, Patent Document 1 discloses that in an internal combustion engine that uses alcohols with low vaporization properties such as ethanol and methanol as fuel, a main injector is installed in each intake port corresponding to each cylinder in the intake passage. At the same time, a cold start injector and a heater are installed at the gathering point upstream of the intake port, and when starting the engine, fuel is injected from the cold start injector and heated by the heater to promote vaporization. This is disclosed.

Microfilm of Utility Model No. 58-92454

Now, when fuel is injected into a collection part such as a surge tank, it is assumed that the entire amount does not reach a specific cylinder and remains in the intake passage. Therefore, from the viewpoint of stability and uniformity of combustion in each cylinder, it is preferable to inject fuel toward each individual cylinder.Also, it is preferable that the vaporized (atomized) fuel touches the inner surface of the intake passage and condenses. - In order to prevent the phenomenon of liquefaction, it is preferable to inject fuel from a location as close to the cylinder as possible.

Therefore, if an injector is installed in each intake port and in the collecting part, during warm-up, fuel is injected into each intake port and injected into the collecting part based on the quality of fuel vaporization in relation to the engine temperature. It is preferable to perform fine control to maintain a balance between fuel injection and fuel injection, thereby achieving both acceleration of vaporization by improving the mixture of fuel and intake air, and combustion stability by direct fuel injection to each intake port. It can be said that there is.

However, in Patent Document 1, the cold start injector and the main injector are used alternatively, and the fuel injection is switched from the cold start injector to the main injector based on a preset reference value. Since it is a switching device, fine-grained control cannot be expected.

Furthermore, when an injector is provided in the gathering part, it is assumed that some of the atomized fuel may come into contact with the inner surface of the intake passage and condense and liquefy before reaching the cylinder, but Patent Document 1 Since the passage from the gathering part to the intake port is horizontal, it is assumed that liquefied fuel will flow into the cylinder along with the flow of intake air, which may reduce the PM suppression effect. be.

The present invention has been made to improve the current situation.

The present invention is
"The intake passage from the throttle valve to each cylinder is composed of a surge tank that communicates with the throttle valve, and a group of branch passages that branch from the surge tank and go to each cylinder, and the locations of each branch passage are A main injector is arranged in each of the surge tanks , an auxiliary injector and an EGR gas inlet are arranged in the surge tank, and an EGR gas passage equipped with an EGR valve is connected to the EGR gas inlet.
This is the basic configuration.

In the above basic configuration, the present invention has the following features:
"Each of the branch passages is formed with a downwardly concave bend, and a heating bypass passage equipped with a heating valve is connected to the EGR gas passage, so that a part of the bypass passage is connected to the EGR gas passage. entering inside the bottom of the bent portion;
Furthermore, it has a control device that controls the auxiliary injector, the main injector, the heating valve, and the EGR valve based on the coolant temperature detected by the coolant temperature sensor, and the control device includes:
When the cooling water temperature is lower than a preset reference value, fuel is injected from both the auxiliary injector and the main injector , and the heating valve is opened to heat the bent portion; while opening the main injector to introduce EGR gas into the surge tank, increasing the fuel injection amount from the main injector as the cooling water temperature increases ;
When the cooling water temperature reaches the reference value, fuel is injected only from the main injector , the heating valve is closed, and heating of the bent portion is stopped.
The structure is as follows.

Note that, in the present invention , EGR gas is injected into the surge tank even when the cooling water temperature reaches the reference value and the auxiliary injector is not used. That is, after the cooling water temperature reaches the reference value, normal control is performed based on the engine speed and load, regardless of the auxiliary injector.

In the present invention, the branch passage includes both a branch pipe formed in the intake manifold and an intake port formed in the cylinder head. Generally, a cylinder has a pair of intake ports, each of which is opened and closed by an intake valve, and the entire intake port may be separated into two parts corresponding to the pair of intake ports, or it may have a single inlet port. There are cases where the injector is branched into two from the middle, and there is a single injector type in which an injector is installed at one inlet, and a dual injector type in which an injector is installed at each of the two branched ports. The invention includes both types.

In addition, the engine temperature is replaced by the cooling water temperature . Since internal combustion engines for automobiles are often equipped with a cooling water temperature sensor as standard, using the cooling water temperature as the engine temperature is advantageous in terms of cost and the like.

In the present invention , since the main injector is always operating, combustion stability and uniformity in each cylinder can be maintained as much as possible. However, when the engine temperature is lower than the reference value, such as during warm-up, the auxiliary injector By injecting fuel from the fuel tank, vaporization of the fuel as a whole can be promoted.

When the engine temperature rises, the vaporization of the fuel also improves, but in the present invention, the amount of injection from the main injector increases as the engine temperature rises, so the necessity of fuel vaporization and the combustion efficiency in each cylinder are reduced. Fine-grained control is possible to balance the need for stability and equalization.

Therefore, the present invention realizes stabilization and equalization of combustion in each cylinder while promoting fuel vaporization and suppressing the amount of PM generated even when the engine temperature is low such as during warm-up operation. can. Further, since fuel vaporization can be promoted even at low temperatures, complete combustion can be promoted, HC, CO, and NOx can be reduced, and it can also contribute to improving fuel efficiency.

In addition, in the present invention, even if the fuel injected into the surge tank and vaporized touches the inner surface of the branch passage and condenses and liquefies (becomes mist) on the way to the cylinder, the liquefied fuel will be stored in the bend. You can leave it there. Therefore, it is possible to prevent or suppress the liquefied fuel from entering the cylinder, thereby preventing or greatly suppressing the generation of PM.

In this case, the fuel accumulated at the bend evaporates due to the flow of intake air and flows into the cylinder, so no particular problem occurs.

Furthermore, when the present invention is adopted, even if liquefied fuel tries to accumulate in the bent portion, it is evaporated by the heating means, so that the vaporization of the fuel is greatly promoted and the effect of preventing PM generation can be enhanced. In addition, since the air-fuel mixture flowing through the bend is heated, vaporization and atomization of the fuel can be promoted to further promote complete combustion.

When the auxiliary injector is provided in the surge tank as in the present invention , since the surge tank has a large volume and the flow of intake air is slow, the mixing properties of fuel and intake air can be greatly improved. First, in this respect, vaporization of the fuel can be promoted. Furthermore, since the fuel is heated by the heat of the EGR gas, the evaporability of the fuel increases and vaporization can be promoted. These two effects can greatly promote vaporization of the fuel.

FIG. 1 is a schematic diagram of an internal combustion engine according to an embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. 1;

(1).Structure of Embodiment Next, an embodiment of the present invention will be described based on the drawings. This embodiment is applied to an internal combustion engine for an automobile. The basic structure of the internal combustion engine is the same as the conventional one, and includes a cylinder block 1 in which a plurality of cylinder bores 2 are formed in the direction of the crankshaft, and a cylinder head 3 fixed to the upper surface of the cylinder block 1.

In the cylinder head 3, a pair of intake ports 4 and an exhaust port 5 are formed, each corresponding to one cylinder bore 2, in line with the crank axis direction, and each of the pair of intake ports 4 has an intake port branch portion. 6 are connected. The pair of intake port branch parts 6 are branched from one intake port collection part 7 that opens on the intake side of the cylinder head 3, and a branch pipe 9 of the intake manifold 8 is connected to each intake port collection part 7. There is.

Needless to say, the intake port 4 is opened and closed by an intake valve 11 driven by an intake valve camshaft 10, and the exhaust port 5 is opened and closed by an exhaust valve driven by an intake valve camshaft (not shown). It is opened and closed by 12. The exhaust port 5a communicates with the exhaust port 5.

A main injector 13 that injects fuel into each intake port branch portion 6 is attached to the cylinder head 3 . The main injector 13 is inserted into a mounting hole 14 formed in the cylinder head 3 via an O-ring, and is arranged at an angle with respect to the cylinder bore axis so that fuel is injected toward the intake port 4. .

The internal combustion engine is equipped with an air cleaner (not shown), and the intake passage starting from the air cleaner includes a throttle valve 15 that controls the amount of intake air, a surge tank 16 to which the throttle valve 15 is fixed, and the above-mentioned passage branched from the surge tank 16. A branch pipe 9 and the previously described intake ports 7 and 6 connected to the branch pipe 9 are provided. The surge tank 16 and the branch pipe 9 constitute an intake manifold 8. In relation to the claims , the branch pipe 9 and the intake ports 7 and 6 constitute a branch passage.

The throttle valve 15 includes a remotely driven electric motor (actuator) 18. An intake duct 19 constituting an intake passage is connected to the inlet of the throttle valve 15, and if the internal combustion engine is not equipped with a supercharger, the intake duct 19 is connected to an air cleaner. On the other hand, when the internal combustion engine is equipped with a supercharger, the intake duct 19 is connected to a discharge port of a compressor housing in the supercharger or an outlet of an intercooler.

Each branch pipe 9 extends downward from the surge tank 16, changes its posture upward, becomes substantially horizontal, and heads toward the cylinder head 3, and its tip is connected to the intake port gathering portion 7 of the cylinder head 3. ing. Therefore, each branch pipe 9 has a downwardly recessed bent portion (downward curved portion) 9a.

The surge tank 16 is integrally formed with a bracket portion 21 having a mounting hole 20 opened into the surge tank 16, and one auxiliary injector 22 is attached to the bracket portion 21. The auxiliary injector 22 is arranged in an inclined position so as to become lower toward the tip. Of course, the orientation can be set arbitrarily, such as horizontal orientation or vertical orientation (downward facing orientation).

Further, although the auxiliary injector 22 is arranged on the side closer to the cylinder head 3 across the axis of the surge tank 16, it may be arranged on the side farther from the cylinder head 3.

Each main injector 13 is attached to a fuel delivery pipe 23 that extends in the direction of the crank axis, and a fuel pipe 24 is connected to the fuel delivery pipe 23 . On the other hand, since there is only one auxiliary injector 22, the fuel pipe 25 is directly connected to the base end of the auxiliary injector 22. It is also possible to arrange the main injectors 13 and the auxiliary injectors 22 close to each other, and to attach each group of main injectors 13 and the auxiliary injectors 22 to one fuel delivery pipe 23 in different positions.

Both injectors 13 and 22 eject fuel using built-in solenoid valves, and plugs 27 are connected to sockets 26 for energizing the solenoid valves. The plug 27 is connected to an ECU (engine control unit) 28 that is a control device.

A catalyst case 29 containing a catalyst is connected to an exhaust outlet hole (not shown) provided on the exhaust side of the cylinder head 3, either directly, via an intake manifold, or via an exhaust turbocharger. When there are multiple exhaust outlet holes corresponding to each cylinder, an exhaust manifold is fixed to the exhaust side surface of the cylinder head 3. When the exhaust gas collecting section is formed inside the cylinder head 3 and only one exhaust outlet hole is open, the catalyst case 29 is directly connected to the exhaust outlet hole via an elbow pipe, or Connected via an exhaust turbocharger.

An EGR passage 31 is branched from a portion of the exhaust passage 30 on the downstream side of the catalyst case 29, and is connected to the surge tank 16. That is, an EGR gas inlet 32 for EGR gas is opened in the surge tank 16 . Further, the EGR passage 31 is provided with an EGR valve 33 that controls the amount of EGR gas passing through.

A bypass passage 34 is branched from a portion of the EGR passage 31 upstream of the EGR valve 33, and the bypass passage 34 is heated to curve upward and intersect with the lower part of each branch pipe 9 (the bottom of the bent portion 9a). A section 35 is provided. Since there are as many heating sections 35 as there are branch pipes 9, communication pipes 36 are provided in the bypass passage 34, which are located upstream and downstream of each heating section 35 and extend long in the crank axis direction. Each heating section 35 is connected to a tube 36.

As shown in FIG. 2, each heating portion 35 is inserted into the bent portion 9a of each branch pipe 9. The group of branch pipes 9 in which the heating portion 35 is integrated in this manner can be manufactured from synthetic resin by joining two parts together.

A heating valve ( heated gas flow rate adjustment valve ) 37 is provided in a portion of the bypass passage 34 upstream of the heating section 35 . The heating valve 37 may have a specification that allows the flow rate to be adjusted stepwise or steplessly, or may have a specification that can be switched between fully open and fully closed.

The downstream end of the bypass passage 34 is connected to the exhaust passage 30, and the EGR gas flowing through the bypass passage 34 is sucked into the exhaust passage 30 by an ejector effect. A check valve 38 is provided in a portion of the bypass passage 34 on the downstream side of the heating section 35 just in case.

The catalyst case 29 is provided with an A/F sensor 39 and an O2 sensor 40, which are connected to the ECU 28. The electric motor 18 of the throttle valve 15, the plug 27 of each injector 13, 22, the EGR valve 33, and the heating valve 37 provided in the bypass passage 34 are also controlled by the ECU 28. Further, the ECU 28 is also connected to an ignition switch 41 and a cooling water temperature sensor 42 that detects the temperature of the cooling water that has passed through the water jacket of the cylinder head 3, for example.

(2). Control aspect The internal combustion engine of the embodiment substitutes the engine temperature with the cooling water temperature, and when the engine is started with the cooling water temperature lower than a preset reference value, the main injector 13 In addition to this injection, fuel is also injected from the auxiliary injector 22.

In this case, the auxiliary injector 22 is provided in the surge tank 16, but since the air-fuel mixture has a long distance to reach the cylinder bore 2, the mixture of fuel and intake air is good. Furthermore, although the surge tank 16 has a large capacity and a low flow rate, this also improves the miscibility of fuel and intake air. Therefore, even when operating in a low temperature environment, vaporization of the fuel can be promoted to promote complete combustion.

When the cooling water temperature is lower than the reference value, the heating valve 37 is open (for example, fully open). Therefore, vaporization of the fuel can be further promoted, and complete combustion can be further promoted. Furthermore, there is a risk that the air-fuel mixture sent from the surge tank 16 may come into contact with the inner surface of the branch pipe 9, causing the vaporized fuel to condense and become a mist. Since the condensed and liquefied fuel 43 accumulates at the bottom of the bent portion 9a, it is possible to prevent or greatly suppress the condensed and mist fuel from flowing into the cylinder bore 2. This also promotes complete combustion.

Moreover, since the heating part 35 through which exhaust gas flows is integrally connected to the bottom of the bending part 9a, even if the vaporized fuel 43 flows down to the bottom of the bending part 9a, it can be immediately evaporated. In this aspect as well, vaporization of the fuel can be promoted to promote complete combustion. In operation when the cooling water is lower than the reference value, the EGR valve 33 is opened and EGR gas is introduced into the surge tank 16. The heat of this EGR gas promotes vaporization of the fuel.

When the main injector 13 and the auxiliary injector 22 are used together, the amount of injection by the main injector 13 is controlled to increase as the cooling water temperature increases. This improves the stability and uniformity of combustion by directly injecting fuel into each cylinder bore 2, and also prevents the generation of harmful substances such as PM, CO, and HC by bringing the combustion closer to complete combustion. can be achieved in a well-balanced manner. Even in this state, the supply of exhaust gas to the heating unit 35 and the supply of EGR gas to the surge tank 16 continue, so that complete combustion by promoting vaporization of the fuel can be ensured.

In this case, the amount of exhaust gas flowing through the bypass passage 34 may be reduced in inverse proportion to the rise in cooling water temperature, or may remain constant. The same applies to the amount of EGR gas introduced into the surge tank 16, and the amount of EGR gas introduced may be decreased in inverse proportion to the rise in cooling water temperature, or may remain constant. It is also possible to control the EGR valve 33 based on signals from the A/F sensor and O2 sensor.

The specific value of the ratio of injection amount between the main injector 13 and the auxiliary injector 22 at which cooling water temperature is determined depends on the amount of heating exhaust gas introduced and the amount of EGR gas in the surge tank 16. It would be a good idea to consider the amount to be introduced and perform tests on actual equipment. In other words, for example, by setting a plurality of temperature ranges and aiming to suppress PM to an allowable amount (PN) in each temperature range, the injection amount by the main injector 13 is increased as much as possible, and the heating exhaust gas is introduced. It is sufficient to select the amount of EGR gas to be introduced into the surge tank 16 and create a control map.

When the temperature of the cooling water exceeds a preset reference value after the warm-up state, fuel is injected only from the main injector 13, the heating valve 37 is closed, and the amount of exhaust gas flowing through the bypass passage 34 becomes zero. Become. On the other hand, the amount of EGR gas introduced into the surge tank 16 is controlled based on a normal control map depending on the engine speed, load, etc.

The heating portion 35 of the bypass passage 34 may be provided with ribs, grooves, etc. to increase the surface area and improve contact with the air-fuel mixture. Providing such a surface area increasing means can promote vaporization of the fuel and promote complete combustion.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the main injector can be provided in each branch pipe of the intake manifold.

The present invention can be embodied in internal combustion engines for automobiles and the like. Therefore, it can be used industrially.

1 Cylinder block 2 Cylinder bore 3 Cylinder head 4 Intake port 6 Intake port branch part forming a branch passage 7 Intake port gathering part forming a branch passage 8 Intake manifold 9 Branch pipe forming a branch passage 9a Bend part 13 Main injector 15 Throttle Valve 16 Surge tank forming a collection passage 22 Auxiliary injector 23 Fuel delivery pipe 28 ECU
29 Catalyst case 31 EGR passage 32 EGR gas inlet 33 EGR valve 34 Bypass passage 35 Heating section 37 Heating valve
42 Cooling water temperature sensor that replaces engine temperature

Claims (1)

The intake passage from the throttle valve to each cylinder is composed of a surge tank communicating with the throttle valve , and a group of branch passages that branch from the surge tank and go to each cylinder, and each of the branch passages has a A main injector is disposed in each of the surge tanks , an auxiliary injector and an EGR gas inlet are disposed in the surge tank, and an EGR gas passage provided with an EGR valve is connected to the EGR gas inlet. hand,
Each of the branch passages is formed with a downwardly concave bent portion, and a heating bypass passage equipped with a heating valve is connected to the EGR gas passage, so that a part of the bypass passage is connected to the EGR gas passage. It has entered the inside of the bottom at the bend,
Furthermore, it has a control device that controls the auxiliary injector, the main injector, the heating valve, and the EGR valve based on the coolant temperature detected by the coolant temperature sensor, and the control device includes:
When the cooling water temperature is lower than a preset reference value, fuel is injected from both the auxiliary injector and the main injector, and the heating valve is opened to heat the bent portion; while opening the main injector to introduce EGR gas into the surge tank, increasing the fuel injection amount from the main injector as the cooling water temperature increases ;
When the cooling water temperature reaches the reference value, fuel is injected only from the main injector, and the heating valve is closed to stop heating the bent portion.
Internal combustion engine.

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