JPH04311623A - Internal combustion engine with supercharger - Google Patents

Abstract

PURPOSE:To provide an internal combustion engine with a supercharger capable of increasing an intake cooling effect more than conventional ones. CONSTITUTION:A supercharger 5, intercooler 7 and throttle valve 9 are provided in an intake path 2 from the upstream side in the mentioned order and constituted such that when an engine load exceeds a predetermined value the opening of the throttle valve 9 is reduced and supercharger discharge pressure is increased by a bypass controlling valve 17 while intake is throttled.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a supercharged internal combustion engine used in an automobile engine, etc., and more particularly to a supercharged internal combustion engine equipped with a means for efficiently cooling engine intake air during supercharging. Concerning internal combustion engines.

0002

2. Description of the Related Art Engines are known in which an intercooler is provided downstream of a supercharger in an intake system to cool intake air. By cooling the high-temperature air compressed by the supercharger with the intercooler, it is possible to improve the intake air filling efficiency of the engine and prevent knocking during high loads. An example of this type of engine is JP-A-60-17
There is one disclosed in Japanese Patent No. 8928. The engine disclosed in the publication includes a mechanical supercharger driven by the engine via an electromagnetic clutch in the intake passage, an intercooler and a throttle valve downstream of the supercharger, and an intake passage upstream of the supercharger. and the intercooler outlet side intake passage are connected by a bypass passage. In this engine, when the load is high, the clutch is turned on to operate the supercharger, and the supercharged air is cooled by the intercooler and supplied to the engine, and when the engine is under low load, the clutch is turned off to stop the supercharger. Air is supplied to the engine from the bypass passage without passing through the supercharger and intercooler. This makes it possible to cool the intake air during supercharging and improve the intake air filling efficiency while preventing the intake air from being supercooled by the intercooler during non-supercharging.

0003

[Problem to be solved by the invention] The above-mentioned Japanese Patent Application Laid-Open No. 60-1
When an intercooler is used to cool the intake air as in the engine disclosed in Japanese Patent No. 78928, the cooling capacity of the intercooler becomes a problem. Usually, the intercooler used is a direct air-cooled type or a water-cooled type that indirectly radiates heat from a radiator to the atmosphere via cooling water. However, when the air temperature is high, either method reduces the cooling capacity and may not be able to maintain the intake air temperature sufficiently low. In addition, the cooling capacity of an intercooler is determined by the heat transfer area of the cooler, so if you try to achieve a sufficiently low intake air temperature, the intercooler may become larger due to an increase in the heat transfer area, and In some cases, it may not be possible to install an intercooler with a desired capacity due to problems or the like. As a result, the intake efficiency of the engine decreases, and it becomes necessary to retard the ignition timing to prevent knocking, which may lead to a decrease in engine performance and fuel consumption. In order to solve the above-mentioned problems, the present invention aims to provide means that can improve the intake air cooling effect without increasing the heat transfer area of the intercooler.

0004

[Means for Solving the Problems] According to the present invention, the supercharger discharge pressure is controlled in an internal combustion engine in which the intake system includes, in order from the upstream side, a supercharger, an intercooler, and an intake throttle valve. A pressure control means is provided, and when the engine load is equal to or higher than a predetermined value, the opening degree of the intake throttle valve is reduced to provide a predetermined intake throttle, and the pressure control means increases the supercharger discharge pressure to control the intake throttle valve. A supercharged internal combustion engine is provided that is characterized in that downstream intake pressure is adjusted according to engine load.

[0005]

[Action] By reducing the opening of the intake throttle valve during high-load operation to provide intake throttle, the intake pressure at the engine inlet (
It is possible to set the supercharger discharge pressure higher than before while keeping the supercharging pressure (supercharging pressure) at the same level as before. When the supercharger discharge pressure is set high, the supercharger discharge temperature increases due to an increase in the compression ratio. This allows the intake air and cooling water (
or cooling air) increases significantly;
The amount of heat transferred in the intercooler can be increased without increasing the heat transfer area, and the cooling effect is improved. The intake air that exits the intercooler passes through the intake throttle valve and expands adiabatically to the same boost pressure as in the past. For this reason, the intake air temperature downstream of the intake throttle valve decreases, but since the intercooler takes away more heat than before, the temperature after expansion also becomes lower than before. Therefore, a lower intake air temperature than the conventional one can be achieved using an intercooler with the same heat transfer area as the conventional one.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the structure of an embodiment of a supercharged internal combustion engine to which the present invention is applied. In the figure, 1 is the engine,
2 is an intake passage of the engine, and 3 is an air cleaner. A supercharger 5 and an intercooler 7 are installed in the intake passage 2 from the air cleaner 3 side (upstream side) to the engine 1 side (downstream side).
, intake throttle valve 9 are arranged in this order.

In this embodiment, a positive displacement compressor is used as the supercharger 5, and a pulley 4 provided on the crankshaft 4 of the engine 1 is used as the supercharger 5.
It is mechanically driven from a through a belt or the like. Further, 6 is an electromagnetic clutch for turning on/off transmission of driving force to the supercharger 5. In this embodiment, the intercooler 7 is of a direct air cooling type, and performs heat exchange between the atmosphere and the supercharger discharge air.

Furthermore, in this embodiment, the intake throttle valve 9 also serves as a throttle valve, and is configured to open to a predetermined degree in accordance with the amount of operation of the accelerator pedal 11 by the driver. 12 is a stroke sensor that detects the amount of operation of the accelerator pedal 11, and 10 is an actuator such as a step motor that drives the throttle valve 9 in response to a signal from an ECU 21, which will be described later.

In this embodiment, the intake throttle valve also serves as the throttle valve, but these may be provided separately. Further, 15 is an intake bypass passage that connects the intake passage on the upstream side of the supercharger 5 and the intake passage on the downstream side of the intercooler 7. A bypass control valve 17 is provided in the intake bypass passage 15 so that the amount of intake air passing through the bypass passage 15 can be adjusted. 18 is an actuator such as a step motor that can continuously change the opening degree of the bypass control valve 17 from fully closed to fully open.

[0010] Reference numeral 21 in the figure is an electronic control unit (ECU) composed of a digital computer. The ECU 21 is an air flow meter 22 installed in the intake passage.
In addition to controlling the fuel injection amount from the fuel injection valve 24 based on the engine intake flow rate, rotation speed, etc. input from the rotation speed sensor 23 provided on the engine crankshaft, the output of the aforementioned accelerator pedal stroke sensor 12 Based on this, the opening degree of the throttle valve 9 is set, and the throttle actuator 10 is controlled to be driven. Also, ECU 2
1 also controls the operation of the supercharger 5 by turning on/off the electromagnetic clutch 6, and controls the opening of the bypass control valve 17 by driving the bypass control valve actuator 18.

FIG. 2 shows the operating line of the electromagnetic clutch 6 of this embodiment. In the figure, the horizontal axis is the engine rotation speed N, and the vertical axis is the intake air amount per engine rotation (Q/N) as a parameter representing the engine load. As can be seen from the figure, in this embodiment, the electromagnetic clutch 6 is turned ON and supercharging is started in a region of medium load or higher.

Further, FIG. 3 shows the opening characteristic of the bypass control valve 17 in this embodiment. Bypass control valve 17
is fully opened in a low load region where the supercharger 5 is not operating, and intake air is supplied to the engine through the bypass passage. In a medium load region or above where the supercharger 5 starts operating, the opening degree of the bypass control valve 17 decreases as the load increases, and in a high load region it becomes fully closed. When the supercharger 5 starts operating, a part of the air discharged from the supercharger 5 passes through the bypass passage 15 to the inlet side of the supercharger 5 and flows back in the opposite direction. By controlling the amount of recirculated air using the bypass control valve 17, the compression ratio of the supercharger can be changed. That is, as shown in FIG. 3, by closing the bypass control valve 17 as the load increases after the supercharger is activated, the supercharger outlet pressure can be greatly increased in accordance with the load.

Next, the opening characteristics of the throttle valve 9 in this embodiment will be explained using FIGS. 4 and 5. In a normal example, the throttle valve is connected to the accelerator pedal by a wire, cable, etc., and the opening degree is proportional to the amount of operation of the accelerator pedal by the driver. However, in this embodiment, the throttle valve 9 and the accelerator pedal 11 are not directly connected, and the operation amount of the accelerator pedal 11 is detected by the accelerator pedal stroke sensor 12, and the ECU 21
controls the throttle valve 9 opening degree by driving the actuator 10 of the throttle valve 9 based on the operation amount. By doing so, the opening characteristic of the throttle valve 9 can be arbitrarily set with respect to the operation amount of the accelerator pedal 11.

In this embodiment, the engine load (Q/N) is set to be proportional to the amount of operation of the accelerator pedal 11, as shown in FIG. When the driver's required load is determined by the operation amount of the accelerator pedal 11, the opening degree of the throttle valve 9 is determined from the relationship shown in FIG. 4 so as to achieve the load. Figure 4 shows the opening degree of throttle valve 9 and engine load (Q/N)
The solid line A represents the opening characteristic of the throttle valve 9 of this embodiment, and the dotted line B represents the conventional general throttle valve opening characteristic.

In the conventional opening characteristic B, the throttle valve opens as the load increases, but the throttle valve 9 of this embodiment
The opening increases linearly so that it becomes fully open at a relatively low load (Fig. 4, section I), and after reaching full open, the opening decreases by a certain amount and then increases again according to the load. (Figure 4, section II). In FIG. 4, the load LS at which the throttle valve opening degree is fully open in section I is set to be equal to the load at which the supercharger 5 starts operating in FIG. 2 and the load at which the bypass control valve 17 begins to close in FIG. 3. . That is, in this embodiment, in section II of FIG. 4, the discharge pressure of the supercharger 5 is increased by the amount by which the throttle valve 9 is throttled, so that the pressure on the downstream side of the throttle valve 9 (supercharging pressure) is made equal to the conventional one. It is maintained.

FIG. 6 shows the relationship between supercharger discharge pressure and load in this embodiment (solid line A) and the conventional example (dotted line B). Load LS
When the supercharger starts operating at , the supercharger discharge pressure P1 rises rapidly. In this example, the speed increasing ratio of the pulley is set higher than before, and the supercharger rotation speed is set higher, so the supercharger discharge pressure is higher than before from the start of operation.
As the load increases, the opening degree of the bypass control valve 17 is reduced, so that it is adjusted to maintain a higher pressure than before. Figure 7
indicates the supercharger discharge temperature T1. Since the discharge pressure P1 is higher than before, the discharge temperature is also higher than before due to the increase in compression ratio.

Next, FIG. 8 shows the intercooler outlet temperature T2 after the supercharger discharge air in FIG. 7 is cooled by the intercooler 7.
shows. At the outlet of the intercooler 7, this embodiment (solid line A)
) and the conventional example (dotted line B) are significantly reduced compared to FIG. This is due to the following reasons. In other words, the amount of heat per unit time (heat flux) q taken by the refrigerant (cooling water or cooling air) in the intercooler 7 is proportional to the product of the heat transfer area S and the difference between the intake air temperature T2 and the refrigerant temperature TC, and q =K×S×(T2-TC). K is the heat transmission coefficient and is a substantially constant value. Therefore, if the heat transfer area S of the intercooler and the coolant temperature TC are constant, the heat flux q increases as the supercharger discharge temperature T2 increases.

In reality, due to the influence of other factors, the heat flux q
is not simply proportional to the temperature difference as described above, but the tendency is the same. Comparing this embodiment with the conventional example, the intake air temperature drop due to passing through the intercooler 7 is greater in this embodiment. Therefore, in this embodiment, intake air can be obtained at the intercooler outlet at a slightly higher temperature and a higher pressure than before. Next, consider the state of intake air on the downstream side of the throttle valve 9. In this embodiment, when the supercharger is in operation, the throttle valve 9 is throttled down compared to the conventional one, and the throttle valve downstream pressure (supercharging pressure) is maintained at the same level as the conventional one. For this reason,
When the intake air passes through the throttle valve 9, it undergoes adiabatic expansion at a higher expansion ratio than before, and the temperature drop due to the adiabatic expansion also increases.

As mentioned above, the intake air temperature T2 on the upstream side of the throttle valve 9 is slightly higher than the conventional one, so as shown in FIG. 9, the intake air temperature T3 (solid line A) on the downstream side of the throttle valve 9 is at this temperature. Due to the drop, the temperature becomes lower than the conventional intake air temperature (dotted line B). Therefore, it is possible to obtain supercharged air at a lower temperature while using an intercooler with the same heat transfer area as the conventional one.

FIGS. 10 and 11 show an embodiment of a flowchart of the above control operation by the ECU 21. Each of these routines is executed by the ECU 21 at regular intervals (for example, every 16 milliseconds). FIG. 10 shows the throttle valve opening control operation. In FIG. 10, when the routine starts, step 100
Then, the operation amount (depression) θA of the accelerator pedal 11 is read from the stroke sensor 12. Next, the driver's requested engine load L0 is calculated from θA using FIG. 5 (step 105), and the opening degree θT of the throttle valve 9 is set based on this L0. Then step 115
Now, output the value of θT set above to the actuator 10 of the throttle valve 9, and change the opening degree of the throttle valve 9 to θ.
Set to T and end the routine.

FIG. 11 shows the boost pressure control operation. In the figure, when the routine is started, in step 200, the engine rotational speed N and the intake air amount Q are read from the rotational speed sensor 23 and the air flow meter 22, respectively. Next, in step 205, the value of Q/N is calculated, and in step 210
Then, the bypass control valve opening degree Qb is set from this Q/N value using FIG. Next, in step 215, the value of Qb set above is output to the actuator 18 of the bypass control valve 17, and the bypass control valve opening degree is set to Qb. Also, in step 220, the rotation speed N and step 2
Based on the Q/N value calculated in step 05, it is determined whether the load condition is in the supercharger operating range using Fig. 2, and if it is in the supercharger operating range, the clutch 6 is turned ON to operate the supercharger. (step 230).

Next, FIG. 12 shows another embodiment of the present invention. This embodiment has approximately the same configuration as the embodiment shown in FIG.
The difference is that a sub-throttle valve 50 that is driven by the engine speed 1 is provided. In this embodiment, the throttle valve 9 is driven by an actuator 10 such as a step motor in order to obtain the opening characteristic shown in FIG. 4, and is not mechanically connected to the accelerator pedal 11. Therefore, in case the step motor 10
There may also be a situation where the throttle valve 9 remains open and becomes inoperable, such as when the throttle valve 9 is out of order. Sub throttle valve 5
0 is provided to ensure that the engine speed can be lowered even in such a situation.

FIG. 13 shows the opening characteristic of the sub-throttle valve 50. The sub-throttle valve 50 opens in proportion to the amount of operation of the accelerator pedal 11, becomes fully open at the accelerator pedal stroke corresponding to the required load LS at which the throttle valve 9 is fully opened, and remains fully open thereafter. Therefore, while the throttle valve 9 is operating normally, the sub-throttle valve 50 does not affect engine control, and the same control as in the embodiment of FIG. 1 is performed. (The dotted line in FIG. 13 is a plot of the throttle pedal opening in FIG. 4 versus the accelerator pedal opening.) The sub-throttle valve 50 is connected to the wire 4.
Since the throttle valve 9 is mechanically connected to the accelerator pedal 11 at 1, even if the throttle valve 9 breaks down, it will surely operate in conjunction with the accelerator pedal 11, closing the intake passage and lowering the engine speed.

FIG. 14 shows the structure of the sub-throttle valve 51. FIG. 14(b) shows a section taken along line BB in FIG. 14(a). The sub-throttle valve 50 includes a plate-shaped valve body 51. A shaft 51a of the valve body 51 passes through the wall surface of the intake passage 2, and an arm 52 is fixed on the outside. Reference numeral 53 indicates the shaft 51a in the direction in which the valve body 51 is fully closed (FIG. 14(a)
) is a return spring that biases counterclockwise). What is shown with 55 and 56 in the figure is the outer wall of the intake passage 2.
They are a cam plate and a wire guide plate that are rotatably mounted around a shaft 57. cam plate 55
The wire guide plate 56 and the wire guide plate 56 are manufactured integrally, and are urged by a return spring 59 to rotate counterclockwise in FIG. 14(a). The wire guide plate 56 also has an accelerator pedal 11.
A wire 41 connected to the wire guide plate 5 is wound around the wire guide plate 5.
6 and the cam plate 55 are designed to rotate together in the clockwise direction.

FIGS. 15(a) to 15(c) show the accelerator pedal 1.
1 shows the state of the valve body 51 when the valve body 51 is operated. FIG. 15a shows the state before the accelerator pedal 11 is depressed. In this state, the valve body 51 connected to the arm 52 is in a fully closed position. When the accelerator pedal 11 is depressed in this state, the cam plate 55 rotates clockwise, and the arm 5
2 rotates clockwise while engaging with the cam surface 55a. Therefore, the valve body 51 begins to open. At this time, the shape of the cam surface 55a is determined so that the opening degree of the valve body 51 increases in proportion to the amount of operation of the accelerator pedal 11. Figure 15
(b) shows a state in which the accelerator pedal is depressed and the valve body 51 of the sub-throttle valve 50 is in the fully open position (Fig. 13
The state of point A) is shown. When the accelerator pedal is further depressed from this state, the arm 55 moves onto the cam surface 55b and moves thereon. However, the cam surface 55b is
Since the valve body 51 is formed to have a curvature that maintains the valve body 2 in the state shown in FIG. 15(b), the valve body 51 maintains the fully open state in this state regardless of the amount of operation of the accelerator pedal 11.

Furthermore, when the accelerator pedal is returned, the cam plate 55 and the arm 52 are forcibly rotated in the valve closing direction by the return springs 59 and 53, respectively, so that the sub-circuit is reliably rotated in response to the return operation of the accelerator pedal. Throttle valve 50 is closed. Therefore, the throttle valve 9
Even in the unlikely event that the actuator 10 fails, the engine rotation can be reliably lowered, and operation in a medium to low load range can be ensured.

[0027]

Effects of the Invention As described above, the supercharged internal combustion engine of the present invention compresses intake air at a higher compression ratio than before in the supercharger operating region to increase the temperature of the intake air. This increases the effective temperature difference between the coolers and enhances the cooling effect of the intake air, making it possible to obtain a lower intake air temperature than before with the same intercooler heat transfer area as before. Therefore, it is possible to further improve the intake air filling efficiency using the same intercooler as in the past, and it is also possible to prevent the occurrence of knocking.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of an internal combustion engine to which the present invention is applied.

FIG. 2 is a diagram illustrating the operating range of the supercharger of the embodiment.

FIG. 3 is a diagram showing the opening characteristic of the bypass control valve of the embodiment.

FIG. 4 is a diagram showing the throttle valve opening characteristics of the same embodiment.

FIG. 5 is a diagram showing the relationship between the accelerator pedal operation amount and the required engine load in the embodiment.

FIG. 6 is a diagram showing supercharger outlet pressure.

FIG. 7 is a diagram showing supercharger outlet temperature.

FIG. 8 is a diagram showing intercooler outlet intake air temperature.

FIG. 9 is a diagram showing the intake air temperature at the inlet of the engine combustion chamber.

FIG. 10 is a flowchart showing throttle valve opening control.

FIG. 11 is a flowchart showing supercharger operation control.

FIG. 12 is a schematic diagram showing the configuration of a second embodiment of the present invention.

FIG. 13 is a diagram showing the sub-throttle valve opening characteristic of the embodiment same as above.

FIG. 14 is a diagram illustrating the structure of a sub-throttle valve.

FIG. 15 is a diagram illustrating the operating state of the sub-throttle valve.

[Explanation of symbols]

1... Engine 2... Intake passage 5... Supercharger 6... Electromagnetic clutch 7... Intercooler 9... Throttle valve 11... Accelerator pedal 15... Bypass passage 17... Bypass control valve 21... Electronic control unit (ECU) 50... Sub-throttle valve

Claims (1)

[Claims] [Claim 1] A supercharger is provided in the intake system in order from the upstream side,
In an internal combustion engine equipped with an intercooler and an intake throttle valve, a pressure control means for controlling the supercharger discharge pressure is provided, and when the engine load is equal to or higher than a predetermined value, the intake throttle valve opening degree is reduced to a predetermined intake throttle value. An internal combustion engine with a supercharger, characterized in that the pressure control means increases the supercharger discharge pressure and adjusts the intake pressure downstream of the intake throttle valve in accordance with the engine load.