JPH0551767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a supercharging pressure control device for an exhaust turbocharger that changes a control target value of supercharging pressure in accordance with the octane number of fuel.

<Background Art> An internal combustion engine with an exhaust turbocharger uses the exhaust energy of the internal combustion engine to rotationally drive an exhaust turbine, and uses a compressor rotated by the exhaust turbine to supercharge intake air to the internal combustion engine. It is known that since the intake air is supercharged to the internal combustion engine, the intake air filling efficiency is improved, and the amount of fuel supplied can be increased accordingly, which greatly contributes to improving the output. However, when the boost pressure becomes excessive, excessive stress acts on the internal combustion engine and its intake/exhaust system, creating a risk of damage or breakage or knocking.

Therefore, one of the preventive measures is, for example, U.S. Patent No.
There is an exhaust flow rate control device found in US Pat. No. 2,947,86. This system is equipped with a flap at the exhaust inlet of the exhaust turbocharger, and by adjusting the degree of opening of the flap, the flow velocity at the exhaust inlet toward the exhaust turbine is controlled, and the exhaust flow velocity is increased in the engine low load rotation region. , the rotational speed of the compressor is increased to increase the boost pressure, and in the high load region of the engine, the opening degree of the flap is increased to reduce the exhaust flow velocity and prevent the exhaust turbine from overspeeding. Prevents excessive rise in supply pressure.

Another method is to provide a bypass passage that connects the upstream and downstream of the exhaust turbine, as seen in Japanese Patent Application Laid-open No. 57-108413, in which the boost pressure downstream of the compressor increases to a predetermined value or higher. When this happens, the bypass control valve device is opened and the exhaust energy is released to the outside via the bypass passage without being used to rotate the exhaust turbine, thereby preventing the exhaust turbine from overspeeding and providing supercharging. Devices that prevent excessive pressure rise are also known.

According to these exhaust flow rate control devices, exhaust bypass control valve devices, etc., which control the flow of exhaust gas led to the exhaust turbine to control the boost pressure, both types of control can cause knocking of the boost pressure. The control target value is determined to set the pressure as high as possible within the range in which the output is maintained.

However, such control target values are set according to a specific type of fuel (for example, regular gasoline), and when using fuel with a higher octane number than this, supercharging will be lower than the set control target value. Although high output can be obtained by increasing the pressure, there is a problem in that the control target value is low and the characteristics of high octane fuel cannot be utilized. Conversely, if a fuel with a lower octane value than the specific fuel is used, knocking will naturally occur since the control target value is set higher than the supercharging pressure for this fuel at which knocking does not occur. This inconvenience arises.

<Object of the Invention> In view of the above-mentioned disadvantages of the conventional exhaust control device, the present invention controls the flow of exhaust gas guided to the exhaust turbine according to the octane number of the fuel used, thereby achieving fine-grained supercharging according to the octane number. It is an object of the present invention to provide a supercharging pressure control device for an exhaust turbocharger that obtains a pressure control target value in a short time, achieves as high output as possible, and prevents knocking.

<Structure of the Invention> For this purpose, the present invention has the following features as shown in FIG.
The octane number detection means precisely detects the octane number of the currently used fuel in a short time, and the control means controls the exhaust control valve according to the octane number and the value detected by the engine operating state detection means, thereby achieving target supercharging according to the octane number. Get pressure.

<Example> Examples of the present invention will be described below based on the drawings.

In the embodiment shown in FIG. 2, the intake air of the internal combustion engine 1 is supplied to the combustion chamber through a passage 2. In the embodiment shown in FIG. During this period, the intake air amount Qa is measured by the air flow meter 3, and the exhaust turbocharger 4
is pressurized (supercharged) by the compressor 5 of
The amount is adjusted by the intake throttle valve 6. Then, it is mixed with fuel injected from the fuel injection valve 7 and introduced into the combustion chamber, where it is combusted to obtain output. The engine rotational speed N at that time is detected by a rotation sensor 8 such as a crank angle sensor.

A pressure sensor 9 is provided in the intake passage 2 between the compressor 5 and the intake throttle valve 6 to detect supercharging pressure Ps.

On the other hand, the combustion exhaust discharged from the combustion chamber of the internal combustion engine 1 into the exhaust passage 11 is transferred to the exhaust turbocharger 4.
The exhaust gas turbine 12 is driven to rotate, and the exhaust gas is discharged to the outside. The exhaust turbine 12 is connected to the compressor 5 by a shaft 4a.
The rotation of the compressor 5 simultaneously drives the compressor 5 to rotate.

Here, the exhaust passage 11 has an exhaust turbine 1
A bypass passage 13 is provided to guide exhaust gas by bypassing 2, and a bypass valve 14 for opening and closing the bypass passage 13 is interposed.

The rotation of the bypass valve 14 is controlled by a bypass valve driving means whose main elements include a diaphragm device 15, a solenoid valve 16, and the like. That is, the diaphragm 15a of the diaphragm device 15 has a link 15b.
A bypass valve 14 is connected through the diaphragm 15a, and supercharging pressure downstream of the compressor 5 is guided through a pressure passage 17 to a pressure working chamber 15c provided on one side of the diaphragm 15a. A three-way switching type solenoid valve 16 is installed in the pressure passage 17, and the supercharging pressure in the pressure passage 17 is relieved to the atmosphere by opening the atmospheric port 16a. The pressure inside the pressure working chamber 15c is increased or decreased by controlling the ratio of opening/closing time of the diaphragm 15.
The valve opening degree of the bypass valve 14 is controlled via the valve a.

A flap 21 is provided in the exhaust passage 11 between the bypass valve 14 and the turbine 12, preferably at the scroll inlet of the exhaust turbine 12, for controlling the exhaust flow rate. The upstream end of the flap 21 is slidably supported by a casing at the scroll inlet of the exhaust turbine 12, and the downstream end swings to increase or decrease the inlet opening area of the exhaust turbine 12. It has become a composition. As the opening area increases (position b shown by the solid line in the figure), the exhaust flow rate decreases, and as the opening degree decreases (position a shown as the dotted line in the figure), the exhaust flow rate increases.

The position of the flap 21 is controlled by a flap drive means whose main components include a diaphragm device 22, a solenoid valve 23, and the like. That is, the diaphragm device 2
A flap 21 is connected to the diaphragm 24 of No. 2 via a link 25, and the diaphragm 2
A pressure passage 27 is provided in a pressure working chamber 26 provided on one side of the
The supercharging pressure is introduced between the compressor 5 and the intake throttle valve 6 via the compressor 5 and the intake throttle valve 6. A three-way switching electromagnetic valve 23 having an atmospheric port 23a is interposed in the pressure passage 27, and supercharging pressure is introduced into the pressure operating chamber 26 by controlling the time ratio of opening and closing the atmospheric port 23a. Control the increase/decrease.

The pressure in the exhaust passage 11 on the upstream side of the flap 21 (exhaust pressure Pe) is detected by an exhaust pressure sensor serving as exhaust pressure detection means. In addition, 6a in the figure is a throttle sensor 2 that detects the opening degree θ of the intake throttle valve 6.
8 is a water temperature sensor that detects the cooling water temperature TW of the internal combustion engine.

These fuel injection valves 7, electromagnetic valves 16, 23 are connected to the pressure sensor 9, which acts as an engine operating state detection means, the throttle sensor 6a, the air flow meter 3, the rotation sensor 8, the water temperature sensor 28, and the starter motor (not shown). The control unit 30 commands and controls the optimum value calculated based on various detection signals output from a starter switch or the like that detects the operation of the starter switch.

Further, the internal combustion engine 1 is provided with a knocking sensor 31 for detecting a knocking level.

In the above embodiment, the exhaust control device for controlling the flow of exhaust gas introduced into the exhaust turbine 12 includes a valve device for controlling the flow rate of exhaust gas supplied to the exhaust turbine, that is, the flap 21, its driving means, and a bypass valve. 14 and its driving means have been disclosed, however, at least one of these may be used.

The control unit 30 is controlled as shown in FIG.

That is, the detection signals of the air flow meter 3 and the rotation sensor 8 are inputted to the intake air amount detection means 41 and the rotation speed detection means 42, where the intake air amount is determined as Qa.
and engine rotational speed N are read and input to the injection pulse calculation means 43.

In the injection pulse calculation means 43, TP=K・Qa/N
A basic injection pulse width TP corresponding to the amount of fuel injected per engine revolution is calculated using the following relational expression, and the output signal is input to the injection pulse correction means 44,
Here, the injector drive pulse is determined by adding various corrections to the basic injection pulse width TP in response to the other engine operating status signals, such as throttle opening θ, engine cooling water temperature Tw, starter switch on/off, etc. It is output to the injection valve driving means 45. The injection valve driving means 45 controls the time ratio of opening and closing of the injection valve 7 according to the input injection pulse width, and injects and supplies the optimum amount of fuel according to the engine operating state.

The basic injection pulse width TP and the engine rotational speed N are input to the flap control duty ratio setting means 46, the bypass valve control duty ratio setting means 52, and the octane number detection means 57, respectively.

The flap control duty ratio setting means 46 reads out the control duty ratio from the memory 49 having a map assigned by the basic injection pulse width TP and the engine rotational speed N, and transmits the value to the driving means 47 of the flap solenoid valve 23. Output. The solenoid valve driving means 47 outputs a driving current having a set duty ratio to drive the flap solenoid valve 23.

The map read by the flap control duty ratio setting means 46 consists of a plurality of maps 48a1 to 48an stored according to the octane number of the fuel used, for example, 91 octane number to 98 octane number, and the octane number of the currently used fuel output from the octane number detection means 57. The map selection means 46a selects and reads one of the maps corresponding to the map.

The operation of the solenoid valve 23 is, for example, at a duty ratio of 0%.
When the pressure control is performed, the atmospheric port 23a is opened to release the pressure in the pressure passage 27 to the atmosphere, and the
6 and displaces the flap 21 to the dotted line position a in the figure via the link 25, thereby reducing the inlet opening area of the exhaust turbine 12, thereby increasing the exhaust flow velocity and increasing the rotation speed of the exhaust turbine 12. do.
When the duty ratio is 100%, the solenoid valve 23 closes the atmospheric port 23a to increase the pressure in the pressure working chamber 26, and displaces the flap 21 via the diaphragm 24 to the open position indicated by the solid line b, thereby closing the inlet of the exhaust turbine 12. The opening area is increased to reduce the exhaust flow velocity and slow down the rotation of the exhaust turbine 12. Therefore, by controlling the control duty ratio of the electromagnetic valve 23, a desired valve opening degree of the flap 21 can be obtained, and the exhaust gas flow rate supplied to the exhaust turbine 12, as well as the boost pressure, can be freely adjusted according to the engine operating state. can be controlled.

The bypass valve control duty ratio setting means 52 reads the control duty ratio from a memory 54 having a plurality of maps 53a1 to 53an corresponding to different fuel octane numbers assigned in advance based on the basic injection pulse width TP and the engine speed N. . In this case, similarly to the flap control, the map selection means 52a selects one of the corresponding octane number maps 53a1 to 53an according to the octane number of the currently used fuel output from the octane number detection means 57.
Select one and read it. Then, the read value is outputted to the driving means 55 of the bypass valve solenoid valve 16 to control the time ratio of opening and closing of the atmospheric port 16a of the solenoid valve 16. Thereby, the valve opening degree of the bypass valve 14 is controlled in the same manner as in the case of flap control. When the opening degree of the bypass valve 14 increases, the exhaust turbine 12 is not rotated and the bypass passage 13 is opened.
An exhaust flow toward the engine is generated, the rotational energy of the exhaust turbine 12 is reduced, the compressor 5 is prevented from over-rotating, and the supercharging pressure can be prevented from increasing excessively.

In this way, the flap control duty ratio setting means 46, the memory 49, and the driving means 47 of the solenoid valve 23 constitute a flap control means, and the bypass valve control duty ratio setting means 52, the driving means 55 of the solenoid valve 16, and the memory 54 constitute a flap control means. constitutes a bypass valve control means, and these as a whole constitute a control means M of the exhaust control device consisting of the flap 21 and the bypass valve 14.

Next, a specific example of the octane number detection means 57 is shown in the block diagram of FIG. 4, and its operation will be explained using the flowchart of FIG.

The octane number detection means 57 in this embodiment is as follows:
This uses an ignition advance control means 60 that controls the ignition circuit 59 of the engine. That is, in the ignition advance control means 60, the basic ignition advance setting means 61 reads the basic ignition advance angle from the memory 63 based on the basic injection pulse width TP and the engine rotational speed N, and outputs it to the ignition advance changing means 64.

The memory 63 has a plurality of basic ignition advance angle maps 62a1 to 62an corresponding to the octane number of the fuel in advance according to the basic injection pulse width TP and the engine rotational speed N, and the current value outputted from the octane number determining means 65, which will be described later. One of the basic ignition advance angle maps 61a1 to 62an corresponding to the octane number of the fuel used is selected via the map selection means 61a.

With the ignition advance control means 60 having such a configuration, first
The basic ignition advance angle map 62a1 for 91 octane is selected to control the ignition circuit 59, and the maps 48a1 and 53a1 for 91 octane are also selected in the flap control duty ratio setting means 46 and the bypass control duty ratio setting means 52. The flap opening degree and the bypass valve opening degree are selected and the boost pressure is controlled respectively (S71).

When the engine is operated and warmed up under such operating conditions, the engine cooling water temperature Tw output from the water temperature sensor 28
Accordingly, the warm-up determination means 66 determines that warm-up is complete (S72), and outputs this to the determination start control means 67.

In the determination start control means 67, based on the basic injection pulse width TP and the engine rotation speed N, the engine rotation speed N is between 2000 rpm and 4000 rpm in S73, and the basic injection pulse width is larger than 7 mm/s in S74. It is determined that the octane number is in the octane determination zone Z shown in FIG. The octane number determination zone Z is in a high speed, high load operating state where knocking is likely to occur. When such an operating state is reached, the ignition advance change means 64 and the octane number determination means 65 are notified of this, and the ignition advance change means 64 changes the basic ignition advance angle (for 91 octane) output from the ignition advance control means 60 in S75. (ignition advance angle) is advanced by 4 degrees to correspond to the basic ignition advance angle for 93 octane (S75) and inputted to the octane number determining means 65. The octane number determination means 65 outputs a command signal to the map selection means 61a to the effect that the 93 octane map should be used, and thereby reads the basic ignition advance angle of the 93 octane map from the corresponding map and changes the ignition circuit 59 to the 93 octane map. Controlled by basic ignition advance angle. Then, it is detected whether knocking occurs in S76 under the ignition advance condition. That is, when knocking occurs, the knocking sensor 31 outputs this to the knocking level detecting means 68, and outputs this to the octane number determining means 65. If notking occurs, it is determined that the selection of the basic ignition advance angle for 93 octane in the ignition advance control means 60 is an error, and it is determined that the currently used fuel is a fuel having an octane number of 91. . And map selection means 6
A command signal indicating that the 91 octane map should be used is output in S78 to 1a, and the 91 octane map is selected for the basic ignition advance angle, flap control duty ratio, and bypass valve control duty ratio, and each control is performed. .

If knotting does not occur in S76,
Furthermore, the ignition advance angle changing means 6 is set so that the ignition advance angle is advanced by 8 degrees from the initial setting basic ignition advance angle for 95 octane number, which is a severe condition for notking.
4 is output to the octane number determining means 65 (S77).

Then, S79 detects whether or not knocking occurs, and if knocking occurs, it is determined that fuel with a lower octane number of 93 is currently being used. The determination results are outputted to the ignition advance control means 60, the flap control duty ratio setting means 46, and the bypass valve control duty ratio setting means 52, respectively, and control is performed using the corresponding map for 93 octane (S80). .

If knocking does not occur in S79, the ignition advance angle is further advanced by 4 degrees and advanced by 12 degrees from the initially set reference ignition advance angle (S81), and whether or not knocking occurs is detected in S82. If knocking occurs, it is determined that 95 octane fuel with a lower octane number is currently being used, and the control means M and ignition advance control means 60 are instructed to control using the 95 octane map. Output.

If knotting does not occur in S82,
It is determined that fuel with an octane rating of 98 is used, which is one rank higher than fuel with an octane rating of 95.

In this way, the exhaust control means M and the ignition advance control means 60 are controlled according to the octane number of the currently used fuel detected by the octane number detection means 57, so that the optimum supercharging pressure that matches the octane number of the currently used fuel is controlled. control and ignition advance control becomes possible.

In this way, for example, if the boost pressure control target value is set to 350 mmHg corresponding to 91 octane fuel (regular gasoline), the same engine can be used with 98 octane fuel (high octane). If you operate the engine, the boost pressure will be adjusted according to the octane number.
Since it is possible to raise the engine power to 465mmHg, it is possible to achieve a significant increase in engine output of about 16%.

After the octane number detection means 57 determines the octane number of the currently used fuel, the determination result is held for a predetermined period of time. The predetermined time period may be a set time period, or may be until the key is turned off or until gasoline is refilled.

In consideration of the case where the octane number of the fuel used was determined in error as described above, the output of the octane number determining means 65 is corrected by the correcting means 69. As shown in Fig. 7, once the ignition advance control and exhaust control are performed in accordance with the detected octane number and the operation is continued, the knocking sensor 31 detects the occurrence of knocking at S91. When this is detected, the ignition advance control means 60
A command signal is issued to delay the advance angle value by 2 degrees (S92). And the result of counting up with S93
If the ignition advance retardation amount RET exceeds 4 degrees in S94, a command is given to select the control map of each duty ratio setting means 46, 52 with an octane value that is one rank lower (S95, S96). . Then, in S97, the flag is set to the ignition advance delay amount RET=0, and the octane number detection operation shown in FIG. 5 is performed again.
Even with this, if it is detected in S91 that knocking has occurred, the above operation is repeated to lower the octane number one by one.

FIG. 8 is a block diagram showing the general functions of the octane number detection means 57 in this embodiment.

<Effects of the Invention> As described above, according to the present invention, the exhaust control device that controls the flow of exhaust gas supplied to the exhaust turbine of the exhaust turbocharger can be operated after precisely detecting the octane number of the currently used fuel in a short time. Control is performed according to the operating conditions and the octane number of the fuel used, and the target boost pressure is obtained according to the octane number, so it is possible to finely control the optimal boost pressure in a short time according to the octane number of the fuel, and it is possible to achieve a low octane number. When using fuel, the supercharging control pressure can be lowered to prevent knocking or engine seizure, and when using high octane fuel, the supercharging control pressure can be maximized to obtain high output. Further, by changing the boost pressure according to the octane number of the fuel, it is possible to increase the compression ratio of the engine without considering variations in the octane number, and it is possible to improve fuel efficiency and output.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 3 is a block diagram showing the operation of the control unit 30 in the same, and Fig. 4 is an octane rating diagram in the same. FIG. 5 is a block diagram showing the detection means, and FIG. 6 is a flowchart showing the operation of the octane number detection means.
The figure is a graph showing octane rating zone Z.
This figure is a flowchart explaining the operation of the correction means 69 in FIG. 4, and FIG. 8 is a block diagram showing the basic structure of an embodiment of the octane number detection means shown in FIG. 4. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Intake passage, 4... Exhaust turbocharger, 5... Compressor, 8... Rotation sensor, 11... Exhaust passage, 12... Exhaust turbine, 13
...Bypass passage, 14...Bypass valve, 16, 23
...Solenoid valve, 21...Flap, 30...Control unit, 31...Knocking sensor, 46...Flap control duty ratio setting means, 46a...Map selection means, 48a1-48an...Map, 52...
Bypass valve control duty ratio setting means, 52a...
Map selection means, 53a1 to 53an...Map,
M...Exhaust control means, 60...Ignition advance control means, 6
1... Basic ignition advance angle setting means, 61a... Map selection means, 62a1 to 62an... Basic ignition advance angle map,
64... Ignition advance angle changing means, 65... Octane number determining means, 67... Judgment start control means, 69... Correction means.

Claims (1)

[Scope of Claims] 1. Engine operating state detection means, octane number detection means that detects the octane number of the currently used fuel by classifying it into three or more levels, and an exhaust system that controls the flow of exhaust gas supplied to the exhaust turbine of the exhaust turbocharger. a control device; and a control means for controlling the exhaust control device according to the engine operating state and the octane number of the fuel used given from the octane number detection means to obtain a target boost pressure, and the octane number detection means comprises: , an ignition advance control means for controlling a basic ignition advance angle based on a basic ignition advance angle set according to the engine operating state and the octane number of the fuel, and a means for detecting the knocking level of the engine to detect the presence or absence of knocking. a basic ignition advance that gradually advances the basic ignition advance controlled by the ignition advance control means within a predetermined range until knocking is detected by the knocking level detection means; ignition angle changing means, a basic ignition advance angle controlled by the ignition advance control means, and a total advance amount changed by the basic ignition advance angle changing means with respect to the basic ignition advance angle. An octane number determination means for determining the octane number of the currently used fuel; and a correction means for correcting the ignition timing or the octane number according to the determined octane number based on the presence or absence of knocking detected after the octane number determination. Features a boost pressure control device for the exhaust turbocharger. 2. Claims characterized in that the exhaust control device is at least one of a valve device that controls the flow rate of exhaust gas supplied to the exhaust turbine of the exhaust turbocharger, and a bypass valve provided in a device that bypasses the exhaust turbine. The supercharging pressure control device for an exhaust turbocharger according to item 1. 3. The supercharging pressure of the exhaust turbocharger according to any one of claims 1 to 2, wherein the octane number detection means is a means for outputting a detection result to the ignition advance control means. Control device.