JP3397902B2 - Engine with turbocharger - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine with a turbocharger configured to scavenging the inside of a combustion chamber while supercharging by a turbocharger.

[0002]

2. Description of the Related Art In engines, especially engines with a supercharger,
Prevention of knocking at low speed and high load is an important issue.
As a means for preventing this knocking, it is effective to effectively scavenge the residual combustion gas in the combustion chamber and lower the temperature in the combustion chamber. In order to perform such scavenging efficiently, the supercharging pressure on the intake side needs to be sufficiently higher than the exhaust pressure. However, in an engine equipped with a turbocharger, since the turbine of the turbocharger is provided on the exhaust side, the exhaust pressure tends to be high, and it has been generally considered difficult to perform efficient scavenging.

Therefore, in Japanese Patent Laid-Open No. 63-297725, an auxiliary exhaust port is opened in the combustion chamber in addition to a normal exhaust port, and a bypass passage bypassing a turbine is connected to the auxiliary exhaust port. It is proposed that an on-off valve is provided in the middle of the bypass passage. In this engine, the valve opening period of the on-off valve is set to a period between the top dead center of the piston and a valve opening period at the intake port and a valve closing period at the exhaust port.

According to this structure, first, the exhaust port is opened to supply a high exhaust pressure to the turbine, thereby increasing the supercharging pressure, and thereafter, opening the auxiliary exhaust port not connected to the turbine to open the exhaust pressure. By fully lowering and opening the intake port during the opening period of this auxiliary exhaust port,
By utilizing a sufficient pressure difference between the boost pressure and the exhaust pressure, sufficient scavenging air can be flowed from the intake port to the auxiliary exhaust port.

[0005]

In the engine of the above publication, highly efficient scavenging can be performed by sufficiently securing the overlap period between the valve opening period at the auxiliary exhaust port and the valve opening period at the intake port. During this period, air-fuel mixture easily blows from the intake port to the auxiliary exhaust port. When such blow-by occurs, fuel efficiency deteriorates and it becomes difficult to obtain a stable air-fuel ratio. On the contrary, if the overlap period is shortened to suppress this blow-through, sufficient scavenging cannot be performed.

As a means for avoiding such an inconvenience, it is conceivable to set the fuel injection period on the intake port side after the closing timing of the auxiliary exhaust port, but even if such a setting is made, the injection before the previous injection is performed. Therefore, it is not possible to prevent the fuel from adhering to the wall of the intake port.

In view of such circumstances, it is an object of the present invention to effectively suppress blow-through of air-fuel mixture in a turbocharged engine while ensuring high scavenging efficiency.

[0008]

As a means for solving the above problems, the present invention is directed to a first exhaust port and a second exhaust port which are opened in a combustion chamber and opened and closed by an exhaust valve,
An intake port that opens in the combustion chamber and is opened and closed by an intake valve; the turbine of the turbocharger is connected only to the first exhaust port; and the compressor of the turbocharger is connected to the intake port. In the turbocharged engine, the first intake port and the second intake port are used as the intake ports.
An intake port is provided, and at least in the low speed operation range,
The valve opening timing and the valve closing timing at the second exhaust port are respectively set later than the valve opening timing and the valve closing timing at the first exhaust port, and the valve opening timing at the second intake port is set to the second exhaust gas. The valve opening timing at the port is set earlier than the valve closing timing, and the valve opening timing at the first intake port is set at a time substantially equal to or later than the valve closing timing at the second exhaust port. The compressor is connected to at least the second intake port, and the fuel injection means is provided for the first intake port (claim 1).

Here, it is more preferable that the valve opening timing at the second intake port is substantially the same as the valve closing timing at the first exhaust port (claim 2), and the valve opening timing at the first intake port is preferable. It is more preferable that the valve timing is substantially the same as the valve closing timing at the second exhaust port (claim 3).

It is more preferable that the flow passage area of the throat portion in the second intake port is set larger than the flow passage area of the throat portion in the first intake port (claim 4). In this case, it becomes more effective by setting the valve opening period at the second intake port longer than the valve opening period at the first intake port (claim 5).

Further, by providing the second exhaust port and the second intake port at positions diagonal to each other, a more excellent effect as will be described later can be obtained (claim 6).

[0012]

According to the engine of the present invention, at least in the low speed operation region, by opening the valve at the first exhaust port, high-pressure exhaust energy (particularly, valve opening at the turbine connected to the first exhaust port is opened. Immediately after the blow-down energy) is supplied, the boost pressure is sufficiently increased by the compressor connected to this turbine. Next, the exhaust pressure is sufficiently reduced by opening the valve in the second exhaust port in addition to the first exhaust port. During the opening period of the second exhaust port, the valve is opened at the second intake port connected to the compressor, so that air is generated with a sufficient pressure difference from the second intake port to the second exhaust port. The flow and the combustion chamber are scavenged. During this period, since the first intake port provided with the fuel injection means has not yet opened, no blow-through of the air-fuel mixture occurs, and there is also a blow-through of fuel adhering to the wall surface of the first intake port in the previous injection. Absent. Then, by opening the first intake port at approximately the same time as or after the closing of the second exhaust port, the air-fuel mixture formed on the first intake port side hardly blows to the exhaust side. It is filled in the combustion chamber.

Here, in the engine according to the second aspect, the second intake port is opened at a timing substantially equal to the valve closing timing at the first exhaust port, so from the beginning of valve opening at the second intake port. The first exhaust port is closed and only the second exhaust port is open. Therefore, a sufficient pressure difference is secured between the supercharging pressure on the intake side and the exhaust pressure over almost the entire opening period of the second intake port.

Further, in the engine according to the third aspect, the first intake port is opened at a time substantially equal to the valve closing time at the second exhaust port, so the first intake port is prevented while preventing the air-fuel mixture from passing through. The maximum valve opening period is secured.

In the above engine, when the engine is lightly loaded without supercharging, the second intake port is burned to the second intake port side during the overlap period between the second intake port open period and the second exhaust port open period. When the gas flows backward and reaches the surge tank, the intake pipe collecting portion, etc., the filled amount in each cylinder cannot be accurately obtained. However, as described in claim 4, the throat portion in the second intake port is described. If the flow passage area is set to be larger than the flow passage area of the throat portion in the first intake port, the volume of the intake system from the second intake port to the surge tank or the like is increased accordingly, and the surge tank It is possible to prevent the burned gas from reaching the etc. with a higher probability.
Further, since the tuning point of the inertial effect shifts to the high speed side by securing a large flow passage area, it is possible to secure a sufficient filling amount even in a high speed operation region where it is generally difficult to obtain a high filling amount.

Further, in the engine according to the fifth aspect, since the valve opening period at the second intake port is set to be longer than the valve opening period at the first intake port, the engine speed is increased in the high speed operation region. 2 It is possible to secure a larger filling amount through the intake port.

In the engine according to the sixth aspect, since the second exhaust port and the second intake port are provided at positions diagonal to each other, the two ports are further separated from each other. Therefore, the scavenging air flows in the combustion chamber from the second intake port toward the second exhaust port for a long distance, and the scavenging efficiency is increased accordingly.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, a first intake port 12 and a second intake port 1 are provided in the combustion chamber of each cylinder 10 of the engine.
4, the first exhaust port 16, and the second exhaust port 18 are open. First intake port 12 and second intake port 1
4 is opened and closed by an intake valve (not shown), and the first exhaust port 16 and the second exhaust port 18 are opened and closed by an exhaust valve (not shown).

A first independent intake pipe 22 is connected to each first intake port 12, a second independent intake pipe 24 is connected to each second intake port 14, and only the first independent intake pipe 24 has fuel. An injection valve 26 is provided. These independent intake pipes 22 and 24 are connected to a common surge tank 20, and a common intake pipe 28 is connected to this surge tank 20. A compressor 30 of the turbocharger is provided in the middle of the common intake pipe 28. The compressor 30 is connected to an exhaust side turbine 34 through a turbo rotating shaft 32 and rotates in conjunction with the turbine 34. Is configured.

In this embodiment, both intake ports 12,
Although the compressor 30 is connected to 14, the present invention only needs to connect the compressor to at least the second intake port.

Each first exhaust port 16 is connected to a first common exhaust pipe 37 via a first exhaust manifold 36, and the turbine 34 is provided in the middle of the first common exhaust pipe 37. An exhaust bypass pipe 40 that connects the upstream side and the downstream side of the turbine 34 by bypassing the turbine 34 is provided in the first common exhaust pipe 37, and a waste gate valve 42 is provided in the middle of the exhaust bypass pipe 40. ing. The waste gate valve 42 is configured to open when the boost pressure on the downstream side of the compressor 30 reaches a certain level or more.

Each second exhaust port 16 is connected to a second common exhaust pipe 39 via a second exhaust manifold 38, and the second common exhaust pipe 39 bypasses the turbine 34. That is, in this engine, the exhaust ports 16, 1
Of the eight, only the first exhaust port 16 is connected to the turbine 34.

FIG. 2 shows the valve opening / closing timings at the ports 12, 14, 16 and 18. The curves IN1 and I in FIG.
N2, EX1 and EX2 represent the following quantities, respectively. Curve IN1: intake valve lift amount curve in the first intake port 12 IN2: intake valve lift amount curve EX in the second intake port 14 EX1: exhaust valve lift amount curve EX2 in the first exhaust port 16: second exhaust port 18 As shown by the exhaust valve lift amount curve EX1 in FIG. 3, the valve opening period in the first exhaust port 16 is set to a period from before the piston bottom dead center to before the piston top dead center. On the other hand, the valve opening period at the second exhaust port 18 is the period from the time point after the piston bottom dead center to the time point after the piston top dead center as shown by the curve EX2. Both the valve timing and the valve closing timing are later than the first exhaust port 16.

As indicated by the curve IN1, the valve opening period at the first intake port 12 is the time point when the next piston bottom dead center is passed from the timing substantially equal to the valve closing timing at the second exhaust port 18. Has been set up to. As shown by the curve IN2, the valve closing timing of the second intake port 14 is the same as the valve closing timing of the first intake port 14, and the valve opening timing is substantially the same as the valve closing timing of the first exhaust port 16. It is said that. Therefore, the valve opening period of the second intake port 14 is longer than that of the first intake port 12.

Next, the operation of this engine will be described.

In each cylinder 10, the first exhaust port 16 is first opened before the piston bottom dead center after the end of the explosion stroke. Since the first exhaust port 16 is connected to the turbine 34 of the turbocharger, high-pressure exhaust gas is supplied to the turbine 34. Therefore, this first exhaust port 1
During the period EO (FIG. 2) from the time when 6 is opened until the time when the second exhaust port 18 is opened, the turbine 34 and the compressor 30 are driven to rotate integrally using the blowdown energy at the initial stage of closing the exhaust valve, The supercharging pressure on the downstream side of the compressor 30 is sufficiently increased.

Next, the second exhaust port 18 is opened,
Since the turbine 34 is not connected to the second exhaust port 18, the exhaust pressure can be sufficiently reduced. Then, during the valve opening period of the second exhaust port 18, the second intake port 14 is opened overlapping with this, and the second intake port 1
Since the supercharging pressure is sufficiently increased on the 4th side as described above, there is a sufficient pressure difference between the supercharging pressure and the exhaust pressure. 2 Sufficient air flows in the combustion chamber toward the exhaust port 18, and the air effectively scavenges the combustion chamber. Moreover,
During the overlap period OL (FIG. 2) in which the scavenging is performed, the first intake port 12 provided with the fuel injection valve 26 has not yet been opened, so even if the second exhaust port 18 is open, the air-fuel mixture is mixed. Of the fuel that has adhered to the wall surface of the first intake port 12 in the previous injection does not occur. Then, the first intake port 12 is opened almost simultaneously with the closing of the second exhaust port 18, so that the mixture is efficiently filled in the combustion chamber through the first intake port 12, and then both intake ports 12, 14 is closed at the same time, and the next explosion stroke comes.

Therefore, according to this engine, it is possible to effectively suppress scavenging of the air-fuel mixture while realizing high-efficiency scavenging in the overlap period OL shown in FIG. Can be prevented.

FIG. 3 shows a simulation result for demonstrating the scavenging effect. In this figure, each line represents the following values. Solid line 46: Supercharging pressure dashed line 48: Exhaust pressure broken line 51 on the side of the first exhaust port 16: BGR (residual gas ratio in the combustion chamber) in a single exhaust port engine without a turbocharger Broken line 52: Turbo BGR polygonal line 53 in the engine equipped with a supercharger and a single exhaust port 53: BGR polygonal line 61 in the engine of the above-mentioned embodiment: Charging efficiency polygonal line 62 in the engine without a turbocharger and a single exhaust port 62: Filling efficiency broken line 63 in the engine equipped with a turbocharger and a single exhaust port: The filling efficiency broken line 63 in the engine of the above embodiment, as shown by the solid line 46 and the broken line 48, It is difficult to make the supercharging pressure higher than the exhaust pressure at the first exhaust port 16, and in particular, when the waste gate valve 42 is provided, the supercharging pressure does not rise above a certain level in the high speed operation region. First exhaust port 1
It will be below the exhaust pressure at 6. However, according to the engine of the above-described embodiment, since the opening period of the second intake port 14 is overlapped in the latter half of the second exhaust port opening period when the exhaust pressure is sufficiently reduced, knocking is particularly likely to occur. A high scavenging effect can be ensured in the low-speed operation range where the scavenging is highly required (the engine speed is about 5000 rpm or less), and in this range, the BGR can be significantly lowered compared to the conventional engine (Fig. The shaded area). Also,
As the scavenging effect is improved, the amount of fresh air filled is increased by the amount of residual gas discharged. Therefore, in the above low-speed operation range, not only the engine without a turbocharger but also a single exhaust equipped with a turbocharger. Even if compared with the engine of the port, the same or higher filling efficiency is obtained.

The present invention is not limited to such an embodiment, and the following modes can be adopted as an example.

(1) In the present invention, the overlap period OL may be secured at least in a low speed operation region (a region where the engine speed is equal to or lower than a certain level), that is, a region where knocking easily occurs, and a high speed at which knocking hardly occurs In the operating region, the overlap OL may be shortened or eliminated by using a variable valve timing mechanism or the like.

(2) In the present invention, the flow passage area of the throat portion in each port may be set freely. However,
In FIG. 1 described above, the flow passage area of the throat portion of the second intake port 14 is set larger than that of the first intake port 12 to thicken the second independent intake pipe 24, and the second intake port 14 in the combustion chamber If the volume of the intake system from the opening to the front of the surge tank 20 is increased, the burned gas in the combustion chamber is temporarily changed to the second intake port 14 during the overlap period OL during light load when supercharging is not performed. Even if it flows back to the side, the probability that this burned gas reaches the surge tank 20 can be greatly reduced, and the inconvenience due to the burned gas entering this surge tank (that is, the air charge amount of each cylinder 10 (Variation) can be avoided more reliably. Further, as the flow path area is increased, the tuning point of the inertial effect can be shifted to the high-speed operation side, which can ensure high filling efficiency not only in the low-speed operation area but also in the high-speed operation area.

(3) The valve closing timings of the first intake port 12 and the second intake port 14 may be set appropriately. However, as shown in the above embodiment, both intake ports 12, 14
If the valve opening period in the second intake port 14 is lengthened by, for example, making the valve closing timing in the same manner, the larger filling amount can be secured even in the high speed operation region.

(4) The valve opening timing of the second intake port 14 may be set earlier than the valve closing timing of the second exhaust port 18 within the range where scavenging is possible. The timing may be near the valve closing timing of the second exhaust port 18 or later. However, if the valve opening timing in the second intake port 14 is set to be approximately the same as the valve closing timing in the first exhaust port 16 as shown in the above embodiment, from the beginning of the opening of the second intake port. There is an advantage that the first exhaust port 16 can be closed and only the second exhaust port 18 can be opened, and highly efficient scavenging can be performed over almost the entire opening period of the second intake port. Further, if the valve opening timing in the first intake port 12 is made substantially equal to the valve closing timing in the second exhaust port 18, the first intake port 1 can be avoided while avoiding blow-through of the air-fuel mixture.
There is an advantage that the valve opening period in 2 can be maximized.

(5) In the present invention, the arrangement position of each port may be set appropriately. However, as shown in FIG.
By disposing the intake port 14 and the second exhaust port 18 at positions diagonal to each other, a larger space can be secured between the ports 14 and 18, and the scavenging air can flow for a longer distance in the combustion chamber. There is an advantage that the scavenging efficiency can be further improved.

[0037]

As described above, according to the present invention, in the turbocharged engine in which the turbine of the turbocharger is connected only to the first exhaust port of the plurality of exhaust ports, the first intake port is used as the intake port. And a second intake port are provided, and the valve opening timing and the valve closing timing at the second exhaust port are respectively set to be later than the valve opening timing and the valve closing timing at the first exhaust port in at least the low speed operation region. 2 The valve opening timing at the intake port is set earlier than the valve closing timing at the second exhaust port, and the valve opening timing at the first intake port is approximately the same as the valve closing timing at the second exhaust port. Alternatively, since the compressor is connected to at least the second intake port and the fuel injection means is provided for the first intake port while setting the timing after that, the opening at the second intake port is performed. During the overlap period between the period and the valve opening period at the second exhaust port, a sufficient pressure difference is secured between the intake side and the exhaust side to perform highly efficient scavenging, and the overlap period is almost completed. By opening the valve at the first intake port from the point in time, it is possible to effectively suppress blow-through of the air-fuel mixture during the overlap period.

Particularly, in the engine according to the second aspect, since the second intake port is opened at a time substantially equal to the valve closing time at the first exhaust port, the intake side is opened from the beginning of valve opening at the second intake port. A sufficient pressure difference can be secured between the supercharging pressure and the exhaust pressure, and more efficient scavenging can be realized over substantially the entire opening period of the second intake port.

Further, in the engine according to the third aspect, the first intake port is opened at a time substantially equal to the valve closing time at the second exhaust port, so that the first intake port of the first intake port is prevented while preventing the air-fuel mixture from passing through. This has the effect of maximizing the valve opening period.

As described in claim 4, the flow passage area of the throat part in the second intake port is set to be larger than the flow passage area of the throat part in the first intake port, so that the surge tank is connected to the surge tank from the second intake port. It is possible to secure a large intake system volume up to and such as to prevent the burned gas from flowing back to the surge tank etc. with a higher probability. This has the effect of preventing the inconvenience, that is, the inconvenience that an accurate filling amount cannot be secured for each cylinder. Further, since the operating region where the filling amount is increased by inertial tuning can be maintained on the high speed side, there is an effect that a sufficient filling amount can be secured even in the high speed operating region.

Further, in the engine according to the fifth aspect, the valve opening period at the second intake port is set to be longer than the valve opening period at the first intake port. This has the effect of ensuring a sufficient amount of filling through the intake port.

In the engine according to the sixth aspect, since the second exhaust port and the second intake port are provided at diagonal positions with respect to each other, both ports can be largely separated from each other, whereby the inside of the combustion chamber can be greatly separated. There is an effect that the scavenging air can be flowed for a longer distance to further improve the scavenging efficiency.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine with a turbocharger according to an embodiment of the present invention.

FIG. 2 is a diagram showing a valve timing set in the engine.

FIG. 3 is a graph showing a simulation result for demonstrating a scavenging effect in the engine.

[Explanation of symbols]

10 cylinders 12 First intake port 14 Second intake port 16 First exhaust port 18 Second exhaust port 22 1st independent intake pipe 24 Second independent intake pipe 26 Fuel injection valve (fuel injection means) 30 compressor 34 turbine 36 First exhaust manifold 38 Second exhaust manifold

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02B 29/08 F02B 37/00 302 F02D 13/02 F02M 69/00 360

Claims (6)

(57) [Claims] 1. A first exhaust port and a second exhaust port which are opened in a combustion chamber and opened and closed by an exhaust valve, and an intake port which is opened in a combustion chamber and opened and closed by an intake valve,
In a turbocharged engine in which a turbine of a turbocharger is connected only to the first exhaust port and a compressor of the turbocharger is connected to the intake port, a first intake port and a first intake port are provided as the intake ports. Two intake ports are provided, and the valve opening timing and the valve closing timing at the second exhaust port are set to be later than the valve opening timing and the valve closing timing at the first exhaust port, respectively, at least in the low speed operation region. The valve opening timing at the intake port is set earlier than the valve closing timing at the second exhaust port, and the valve opening timing at the first intake port is approximately the same as the valve closing timing at the second exhaust port. Or a later time, the compressor is connected to at least the second intake port, and fuel injection means is provided for the first intake port. That engine with a turbocharger. 2. The turbocharged engine according to claim 1, wherein the valve opening timing at the second intake port is set to the first
An engine with a turbocharger, which is set at a time that is almost the same as the valve closing time at the exhaust port. 3. The turbocharged engine according to claim 1 or 2, wherein the valve opening timing at the first intake port is set to be substantially the same as the valve closing timing at the second exhaust port. An engine with a turbocharger. 4. The turbocharged engine according to claim 1, wherein the throat section flow passage area in the second intake port is larger than the throat section flow passage area in the first intake port. The turbocharged engine characterized by the setting. 5. The turbocharged engine according to claim 1, wherein the valve opening period at the second intake port is set longer than the valve opening period at the first intake port. An engine with a turbocharger. 6. The turbocharged engine according to claim 1, wherein the second exhaust port and the second exhaust port are provided.
An engine with a turbocharger characterized in that the intake port and the intake port are provided at diagonal positions.