JPH0745824B2 - Turbocharged engine - Google Patents

Description

The present invention relates to a turbocharged engine.

(Prior Art) Conventionally, in order to increase the output of an engine, a supercharger such as a turbocharger has been widely put into practical use.

By the way, generally, in a 4-cycle engine, the valve opening periods of the intake valve and the exhaust valve overlap for a predetermined period. This overlap period is inevitably generated as a result of prolonging the opening time of the intake valve in order to improve the charging efficiency of intake air particularly when the engine is under high load.

However, because of the above-mentioned overlap period, that is, because the intake valve opens for a predetermined time at the end of the exhaust stroke, the combustion gas in the combustion chamber is discharged when the pressure in the intake passage is low (the negative pressure is large) and the load is low. Flows back in. When such a backflow of combustion gas occurs, the backflow combustion gas is again sucked into the combustion chamber along with the intake air in the next intake stroke, and the backflow of the combustion gas lowers the pressure itself in the combustion chamber, resulting in sufficient exhaust gas. The combustion gas remains in the combustion chamber and deteriorates the combustion performance. There is also a problem that the intake compression temperature rises excessively due to the mixture of the residual combustion gas, which causes explosive combustion at an inappropriate time, that is, so-called knocking easily occurs.

Therefore, in order to deal with this problem, a main intake valve that has two types of main and sub intake passages and does not have the above-described valve opening overlap period with the exhaust valve for the main intake passage of the engine is provided. On the other hand, a secondary intake valve having a valve opening overlap period with the exhaust valve and a rotary valve are provided in the secondary intake passage, and the rotary valve is closed to close the main intake valve when the load is low such that backflow of the combustion gas is likely to occur. There is a conventional technique in which the backflow of the residual combustion gas is prevented by inhaling air only from the inside (see, for example, Japanese Utility Model Laid-Open No. 56-142226).

However, in this conventional technique, since the opening timing of the auxiliary intake valve is constant as described above, the timing of starting the intake from the auxiliary intake passage is also constant, and therefore the intake start timing corresponding to the load is changed. I can't change it, so
It is not always possible to effectively prevent the backflow.

Therefore, in order to solve the above-mentioned drawbacks of the prior art, a timing valve in which the intake passage of the engine is opened later than the intake valve in addition to the intake valve, and the delay amount (delay angle value) is variable It is proposed that the timing valve be opened at a crank angle at which the pressures of the upstream side and the downstream side of the timing valve in the intake passage match at least when the engine is under a low load. See Japanese Patent Application No. Sho 60-91702 concerning the prior application). According to the above configuration, the intake passage is opened when the pressure on the upstream side of the timing valve, that is, the pressure in the intake passage becomes equal to the pressure on the downstream side of the timing valve, that is, the pressure in the combustion chamber. Therefore, the reverse flow of the residual gas in the combustion chamber into the intake passage is prevented even during the opening period of the intake valve.

As described above, in the above configuration, the delay of the intake passage opening timing, that is, the retard value is determined by the difference between the intake pipe internal pressure and the exhaust pressure.

When the timing valve as in the above-mentioned prior application is provided, even after the intake valve is opened, intake of intake air is not substantially started for a predetermined period until the timing valve is opened, and the combustion chamber The amount of work consumed to inhale the intake air is reduced by that amount, and the piston downward motion is assisted by the pressure of the residual gas (pumping loss reduction effect).

(Problems to be Solved by the Invention) However, when the invention of the prior application is applied to the engine with the turbocharger, the following consideration is required.

That is, in the case of an engine equipped with a turbocharger,
In the light load region where the turbocharger does not have the supercharging action, the same action as above can be obtained, but on the other hand, in the high load region where the supercharging action occurs (when the intake pipe pressure becomes a positive pressure equal to or higher than the atmospheric pressure, As shown in FIG. 9, there is a region where the pressure difference between the intake pipe internal pressure and the exhaust pressure rises as the supercharging pressure rises. Therefore, in such a region, the above-mentioned retard angle is originally determined according to the increase amount of the supercharging pressure itself. It is desirable to increase the value.

On the other hand, even in the case of a diesel engine equipped with a turbocharger, as shown in the characteristics of Fig. 10, the pressure difference between the exhaust pressure and the intake pipe internal pressure increases with the increase of the intake pipe internal pressure according to the load amount. Therefore, it is better to increase the retard angle value as the supercharging pressure increases. Note that, in general,
As shown in Fig. 11, when the engine exhaust pressure rises relative to the intake pipe pressure as shown in a, b, and c, the required opening timing of the intake passage is It will be gradually delayed by A, B and C accordingly.

Therefore, also from this point of view, in the engine with the intake start timing control timing valve in the intake passage, and in the engine with the supercharger, it is possible to control the timing valve opening retard value according to the supercharging pressure (load amount). preferable.

Of course, in the engine with a supercharger as described above, an exhaust bypass passage equipped with a waste gate valve is provided, and the waste gate valve is opened according to the rise of the supercharging pressure to bypass the exhaust gas, and the target The supercharging pressure is controlled, but in the high supercharging region where the waste gate valve is opened in this way, the above point becomes a problem.

(Means for Solving Problems) The present invention has been made in view of the above points, and an exhaust passage is provided with an exhaust turbine having a waste gate valve and an exhaust bias passage, while an intake passage is provided. A supercharging compressor driven by the exhaust turbine is provided,
In a turbocharged engine that performs intake supercharging by the supercharging compressor and opens the wastegate valve in response to increase in supercharging pressure to increase the amount of exhaust bias, set the intake start timing of the cylinder of the engine. Intake timing delay means for delaying a predetermined delay angle, and delay for increasing the delay angle of the intake start timing according to the rise of the supercharging pressure in at least the opening operation region of the waste gate valve in the supercharging operation region of the engine. The angle control means is provided.

(Operation) According to the above means, the delay angle of the intake timing delay means for delaying the intake start timing of the engine is set by the delay angle control means in at least the supercharging operation region where the waste gate valve is opened. The control is performed so as to increase as the supercharging pressure of the supercharger rises. Therefore, control is performed according to the pressure difference between the exhaust pressure and the intake pipe internal pressure, which increases as the supercharging pressure rises, that is, the load increases. It is possible to control the increase of the retard angle value according to the increase of the supercharging pressure, and the residual combustion gas increases. It is possible to prevent backflow of gas, effectively reduce the amount of residual combustion gas, and reduce pumping loss. As a result, the output improving effect is enhanced.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 2 to 8.

First, FIG. 2 shows a 4-cylinder 4-cycle engine E with a turbocharger according to an embodiment of the present invention. The engine body 1 of the engine E has four cylinders 20A,
20B, 20C, 20D are arranged in a row. The cylinder head 2 of the engine body 1 has an exhaust passage 3 and an exhaust passage 4 respectively formed in an intake passage communicating with the combustion chambers 18, 18 ,. The intake port 16 of the intake passage 3 facing the combustion chamber 18 is opened and closed by an intake valve, and the exhaust port 17 of the exhaust passage 4 facing the combustion chamber 8 is opened and closed by an exhaust valve. Further, reference numeral 8 is a fuel injector.

An intake manifold 7 is connected to the outer ends of the intake passages 3, 3 ... of the cylinders 20A, 20B. The intake manifold 7 is a cylinder formed by merging four branch passage portions 14, 14 ... For branching to the cylinders 20A, 20B. The collecting passage portion 13 and the main passage portion 15 connected to the intake upstream side of the collecting passage portion 13 are composed of three parts. Further, in the main passage portion 15, the air cleaner 23 and the air flow meter 22 are further provided at the most upstream end of the intake air via the compressor casing 62 of the turbocharger 60, and the throttle valve 25 is provided near the downstream end. . A compressor wheel 64 is provided in the compressor casing 62 of the turbocharger 60.

Further, in the inside of the collecting passage portion 13 of the intake manifold 7, there is provided a rotary valve which is composed of a cylindrical body and is rotated in synchronization with the engine rotation as will be described later in detail. (Applicable) 10 is fitted. This rotary valve 10 has 4
It is provided with one valve dividing section 10A, 10B, 10C, 10D, and these valve dividing sections 10A, 10B, which open and close in synchronization with the rotation of the engine as described above.
By the action of 10C and 10D, the branch passage portions 14, 14 ... Of the cylinders 20A, 20B ... Are sequentially and selectively connected to the main passage portion 15 side. And, for that purpose, the opening ends 14a, 14a of the branch passage portions 14, 14 ...
The rectangular ports 11, 11 ... Each having a predetermined opening area are formed at positions corresponding to. Therefore,
Each of the branch valves 10A, 1B, 10C, 10D of the rotary valve 10 has its ports 11, 11 ... in the branch passages 14, 14, ... It will be opened correspondingly.

On the other hand, reference numeral 30 is a bypass passage for connecting the main passage portion 15 immediately after the throttle valve 25 and the branch passage portions 14, 14, ... to each other, and the branch passage portions 14 downstream of the bypass passage 30. By-pass control valves 31, 31, ... Are provided coaxially in the communicating portion with the 14, 14 ,. The open / close state of these bypass control valves 31, 31, ... Is controlled by the bypass actuator 32. The bypass actuator 32 operates by a control signal from the engine control unit 40 as described later, and opens the bypass control valves 31, 31 ... When the engine speed and the load amount exceed a predetermined value. It bypasses 10 and acts to increase the amount of intake air with good response.

On the other hand, the rotary shaft 10a of the rotary valve 10 is connected to a pulley 39 via a rotary valve control device 34, which will be described in detail later. The pulley 39 is connected via a belt 19 to a drive pulley 45 attached to the end of the engine crankshaft 26, and the rotary valve 10 is adapted to rotate in synchronization with the engine crankshaft 26. . A rotary valve control device (corresponding to delay angle control means in the claims) 34 includes a sixteenth helical gear 37 attached to an end of a rotary shaft 35a of a pulley 39, and the rotary valve 10 rotary shaft 10a. Second helical gear 36 mounted on the end
And an adjusting piece 46 that meshes with both helical gears 37 and 36. The adjusting piece 46 is configured so that the meshing position with the first helical gear 37 and the second helical gear 36 can be arbitrarily changed in the rotation axis direction of the rotary valve 10 so that the adjustment piece 46 moves in the rotation axis direction. When the meshing position changes, the relative rotational position between the helical gears 37, 36 changes, which changes the opening / closing timing advance angle amount (retard angle amount) of the rotary valve 10. An adjusting actuator 43 is provided for adjusting one of the adjusting pieces 46 in the axial direction, and the adjusting actuator 43 is operated by a control signal from an engine control unit 40 configured by incorporating a microcomputer. It has become. The engine control unit 40 is adapted to receive the detection signal of the engine speed detecting means 42.
Determines the amount of low tie valve retardation control according to the engine speed detection signal, and drives the rotary valve control device 34 via the adjustment actuator 43. Further, the engine control unit 40 is also adapted to receive a detection signal of an engine load detecting means (not shown),
The engine control unit 40 uses the bypass control valve according to the value of the engine speed and the engine load.
A command signal for opening the bypass control valves 31, 31, ... Is output to the bypass actuators 31, 31 ,. Further, the engine control unit 40 also receives the intake pipe internal pressure detected by the intake pipe internal pressure detection means 44 and the exhaust pressure detection value detected by an exhaust pressure sensor 70 provided in the exhaust manifold 54 part described later, respectively. The engine control unit 40 controls the rotary valve 10 based on the values of the engine speed and the intake pipe internal pressure, as will be described later.

On the other hand, an exhaust branch pipe 54 is connected to the exhaust passage 4 of each cylinder. Then, the collecting portion of each exhaust branch pipe 54
The inlet side of the turbine casing 61 of the turbocharger 60 is connected to the turbocharger 60, and is connected to the exhaust pipe 55 via the turbine casing 61. Also the above turbine casing
Inside the 61, a turbine wheel 63 is provided. The turbine wheel 63 is integrally connected to a compressor wheel 64 provided inside the compressor casing 62 on the main intake passage 15 side by a rotary shaft 65, and the turbine wheel 63 rotationally driven by exhaust gas causes the turbine wheel 63 to rotate. The wheel 64 is driven to supercharge intake air.

Further, reference numeral 51 is, for example, an electronically controlled wastegate valve provided in an exhaust bypass passage bypassing the turbine casing 61 and controlled by the engine control unit 40.
It is designed to be driven by, and along with the adjustment of the normal target supercharging pressure, for example, during acceleration, the waste gate of the exhaust bypass passage is opened excessively to reduce exhaust resistance,
Functions such as improving acceleration performance. Then, at least in the high supercharging region where the waste gate valve 51 is opened, the rotary valve 10 is controlled in accordance with the rise of the supercharging pressure to delay the intake timing to remove the residual combustion gas, as will be described later. Is controlled, and the amount of fresh air is relatively increased to increase the output.

Reference numeral 56 is a knocking sensor, which detects the occurrence of knocking of the engine E and supplies the detection signal to the engine control unit 40.

Here, the basic relationship between the opening / closing timing of the intake valve and the exhaust valve and the opening / closing timing of the rotary valve 10 in the illustrated embodiment will be described with reference to FIG. As shown by the curve S in FIG.
The piston top dead center begins to open (TDC) from a predetermined crank angle earlier theta _S, closed piston bottom dead center than (BDC) in a predetermined crank angle late theta _{S '.}

On the other hand, the rotary valve 10 has its opening / closing timing changed by the action of the rotary valve control device 34,
Basically, as shown by the curve R in FIG. 4, the rotary valve 10 is later than the intake valve opening timing θ _S by a predetermined time (TD
The valve starts opening at θ _{R (} later than C) and closes at a timing θ _A ′ that is greater than the intake valve closing timing θ _S ′.

As described above, the rotary valve 10 normally starts to open after a predetermined crank angle (Δθ) from the valve opening timing θ _S of the intake valve. However, in the present specification, the rotary valve 10 is opened. The valve opening delay operation is referred to as a retard angle, and the valve opening delay amount (crank angle) Δθ is referred to as a retard value. By the way, the above-mentioned rotary valve control device 34 uses the retard value Δθ.
Is to control.

In the illustrated embodiment, the exhaust valve is closed at a timing θ _E ′ slightly delayed from TDC, as indicated by the curve E in FIG.

Next, the retard control operation of the rotary valve 10 by the engine control unit 40 will be described with reference to the flowchart of FIG. 3. In this control example, it is determined whether or not the rotary valve 10 is controlled to open / close at an appropriate timing. Not only the engine speed N and the intake pipe pressure P,
The presence or absence of knocking is also determined as a parameter.

That is, first, at step S ₁ , the engine speed N and the intake pressure (intake pipe internal pressure) P are input. Then, the process proceeds to step S _2, the rotary valve based on the value of the engine speed N and the intake pressure P input in step S ₁
Calculate the retard value Δθ of 10. A method of calculating the retard value Δθ will be described here. FIG. 6 (a) shows a map of the rotary valve retard value Δθ when the engine is a gasoline engine, and FIG. 6 (b) shows the map of the engine. The rotary valve retardation value Δθ for a diesel engine is shown. Both maps of FIGS. 6 (a) and 6 (b) will be described below. First, in the case of the gasoline engine shown in FIG. 6 (a), an effective intake region (a period during which the intake action is substantially performed, The lower the speed is, the smaller the area becomes because the actual air supply time becomes shorter for the same crank angle range.)
In the low to medium speed range where there is no problem with the above, the opening timing of the rotary valve 10 is advanced as the load is increased as shown by an arrow X ₁ in FIG. In the region, the opening timing of the rotary valve 10 is delayed (the retard angle value Δθ increases) as the load increases, as indicated by arrows X ₂ and X ₃ .

Next, a description will be given of the high-speed region where the effective intake region is particularly problematic. In this region, the intake amount is prioritized. Therefore, the retard angle value Δθ depends on the engine speed rather than the load. As shown by arrow X ₄ in Fig. 6 (a), the rotary valve delay value Δθ becomes smaller (the valve opening timing is earlier) as the engine speed increases regardless of the engine load. In addition, the retard angle value Δθ becomes a constant minimum value at a predetermined rotation speed or more (hatched portion). FIG. 5 shows the state of the minimum retardation value (Δθ = Δθmin). In this state, the rotary valve 10 is opened (θ _R ) almost at the same time as the exhaust valve is closed (θ _E ′). Like

Next, the case of the diesel engine shown in FIG. 6 (b) will be explained. In this case, in the low and medium speed range, FIG. 6 (b) corresponds to the pressure characteristic of the diesel engine shown in FIG. As the engine load increases, the retard value Δθ of the rotary valve is increased as indicated by the arrow X _{5 in} the middle, while in the high-speed range where the effective intake region becomes a problem, FIG. 6 (a)
Almost the same as for the gasoline engine of
₆ ). Further determining occurrence of knocking proceeds to step S _3. As a result, in the case of YES, it is determined that knocking occurs because the opening timing of the rotary valve 10 is too early with the retard value Δθ calculated as described above, and then step S ₄ In order to suppress the knocking, the retard angle value Δθ of the rotary valve 10 calculated in step S ₂ is increased by Δθ + Δθ ′.
Set to. Then, in the next step S ₅ , the set advance value Δ
The control device 34 of the rotary valve 10 is operated at θ + Δθ ′.

On the other hand, if the determination result in step S ₃ is NO, that is, if knocking has not occurred, the retard value Δθ of the rotary valve calculated in step S ₂ is determined to be appropriate, and step S ₅ is performed as it is. Then, the rotary valve control device 34 is operated with the retard value Δθ of the rotary valve 10 calculated in step S ₂ .

In the above case, as shown in the embodiment of FIG. 2, when the wastegate valve 51 is opened at the time of acceleration to lower the exhaust pressure and improve the acceleration response, It goes without saying that the retard value Δθ of the steady map in the above flowchart is changed and corrected accordingly.

By the way, to explain why knocking is controlled by increasing the retardation value Δθ of the rotary valve when knocking occurs, it is because of a large differential pressure between the upstream side of the rotary valve and the combustion chamber due to the opening delay of the rotary valve. Is generated (hatched portion in FIG. 8), and the differential pressure increases the intake turbulence in the combustion chamber after the rotary valve is opened and suppresses the local temperature rise of intake that causes knocking. It is a thing.

FIG. 7 shows the retard value Δθ of the rotary valve 10 as described above.
It is a description of what kind of operation and effect can be obtained by controlling the engine by dividing it by the operating region of the engine.
In the region indicated by reference symbol Z ₁ in the figure (low-medium speed region), mainly the pumping loss reduction effect and the residual combustion gas reduction effect (B)
It is shown that the effect (A) of securing the effective intake area is mainly obtained in the area (high speed area) indicated by reference numeral Z ₂ .

As described above, the present invention provides the exhaust passage with the exhaust valve having the waste valve and the exhaust bypass passage, while the intake passage has the exhaust turbine driven by the exhaust turbine. In a turbocharged engine in which a compressor is provided, intake supercharging is performed by the supercharging compressor, and the wastegate valve is opened to increase the exhaust gas bypass amount in response to a rise in supercharging pressure, An intake timing delay means for delaying the intake start timing by a predetermined delay angle, and a delay angle of the intake start timing in accordance with an increase in the supercharging pressure at least in the opening operation region of the waste gate valve in the supercharging operation region of the engine. And a delay angle control means for increasing the delay time are provided.

Therefore, according to the present invention, at least in the high supercharging operation region in which the waste gate valve is opened, the delay angle of the intake timing delay means for delaying the intake start timing of the engine is controlled by the delay angle control means. The control is performed so that it increases as the supercharging pressure of the machine rises.Therefore, control is performed according to the pressure difference between the exhaust pressure and the intake pipe internal pressure, which increases as the supercharging pressure rises. It is possible to control the increase of the angular value, the supercharging pressure is high, and the amount of fresh combustion gas increases, so that the amount of fresh air filling decreases relatively, and the reverse flow of combustion gas occurs even in the supercharging region where output loss occurs. It becomes possible to effectively reduce the amount of residual combustion gas and to reduce pumping loss. As a result, the output improving effect is enhanced.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a schematic plan view of a turbocharged engine according to an embodiment of the present invention, and FIG.
FIG. 4 is a flowchart showing the control operation of the engine control unit of the engine, FIGS. 4 and 5 are time charts showing the operation timing of the rotary valve,
6 (a) and 6 (b) are map characteristic diagrams of the rotary valve retard value Δθ used in the control operation of FIG. 3, and FIG. 7 is an action characteristic corresponding to the engine operating region of the engine. FIG. 8 is a control characteristic diagram of the engine when knocking occurs, and FIGS. 9 to 11 are intake and exhaust pressure characteristic diagrams for explaining the problems of the conventional turbocharged engine. . E …… Engine 3 …… Intake passage 4 …… Exhaust passage 10 …… Rotary valve 15 …… Main intake passage 20A ～ 20B …… Cylinder 34 …… Rotary valve control device 40 …… Engine control unit 42 …… Engine rotation Number detecting means 44 …… Intake pipe pressure detecting means 54 …… Exhaust manifold 60 …… Turbocharger 63 …… Turbine wheel 64 …… Compressor wheel

Claims (1)

[Claims] 1. An exhaust passage is provided with an exhaust turbine having a wastegate valve and an exhaust bypass passage,
A supercharging compressor driven by the exhaust turbine is provided in the intake passage, the supercharging compressor performs intake supercharging, and the wastegate valve is opened in response to a rise in supercharging pressure to exhaust the exhaust bias amount. In a turbocharged engine for increasing the engine charge, the intake timing delay means for delaying the intake start timing of the cylinder of the engine by a predetermined delay angle, and the supercharge operation area of the engine at least in the opening operation area of the waste gate valve concerned. A turbocharged engine, comprising: delay angle control means for increasing a delay angle of the intake start timing in accordance with an increase in supply pressure.