JPH0749774B2 - Supercharging pressure control method - Google Patents

Description

The present invention relates to a supercharging pressure control method for an internal combustion engine equipped with a supercharger.

[Conventional technology and problems]

In an engine equipped with a supercharger, an upper limit value of the supercharging pressure is generally set, and even if the supercharging pressure at the upper limit value is maintained for a long time, the value is set so that no problem occurs in the engine and the supercharger. It is selected. However, for a short time, there is no particular problem even if the boost pressure is maintained above this upper limit,
As a result, Japanese Patent Laid-Open No. 57-157017 proposes to increase the upper limit value of the supercharging pressure only when the engine is suddenly accelerated to realize good vehicle acceleration performance.

However, during sudden engine acceleration, if the supercharging pressure rises above the normal upper limit when the throttle valve opening is close to full opening, the engine load will rise abnormally and the engine may be damaged even for a short time. There is a nature.

[Means for solving problems]

In the supercharging pressure control method according to the present invention, the upper limit value of the supercharging pressure is set to the first set value except when the engine is rapidly accelerated, and the upper limit value of the supercharging pressure is set to the second value from the first set value when the engine is rapidly accelerated. In the supercharging pressure control method of increasing the value to the above value, the upper limit value of the supercharging pressure is decreased from the second set value when the engine load exceeds a predetermined value during the rapid engine acceleration.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows an internal combustion engine to which an embodiment of the present invention is applied.
In this figure, a piston 12 is slidably supported in a cylinder bore 11 formed in an engine body 10, and a combustion chamber 13 is formed above the piston 12. An intake passage 14 and an exhaust passage 15 communicate with the combustion chamber 13. An intake port 24 extending from the combustion chamber 13 and connected to the intake passage 14 is opened and closed by an intake valve 25, and an exhaust port 26 extending from the combustion chamber 13 and connected to the exhaust passage 15 is opened and closed by an exhaust valve 27.

The air cleaner 16 is provided on the most upstream side of the intake passage 14,
The air flow meter 17 is provided on the downstream side. A compressor 19 of the turbocharger 18 is provided further downstream, and a throttle valve 20 is provided downstream of the compressor 19.
Is provided. The throttle valve 20 changes the inner flow passage area of the intake passage 14 in conjunction with an access pedal (not shown).
A surge tank is located in the intake passage 14 downstream of the throttle valve 20.
21 is formed.

Turbine 41 of turbocharger 18 is provided in the middle of exhaust passage 15.
And a bypass passage 42 that bypasses the turbine 41 is formed. In the turbocharger 18, the turbine 41 is rotationally driven by the exhaust gas passing through the exhaust passage 15, whereby the compressor 19 is rotated and the pressure of the air sucked from the intake passage 14 is increased. The waste gate valve 43 opens and closes the bypass passage 42 to open the turbine 41.
Adjust the amount of exhaust gas supplied to the turbocharger
Controls 18 rotations. The actuator 50 that drives the wastegate valve 43 to open and close has a conventionally known structure, and the inside of the shell 51 is partitioned by the diaphragm 52 to form a pressure chamber.
53 is formed, and the pressure immediately downstream of the compressor 19 in the intake passage 14 is transmitted into the pressure chamber 53 via the passage 54. Then, the pressure in the pressure chamber 53 is
When the elastic force of 55 is overcome, the waste gate valve 43 opens the bypass passage 42, suppresses the exhaust gas passing through the turbine 41, and makes the outlet pressure of the compressor 19 of the turbocharger 18 constant.

A passage 56 that branches from the middle of the passage 54 communicates with the intake passage 14 upstream of the compressor 19, and a supercharging pressure control valve 57 and a throttle 58 are provided in the middle of the passage 56. The supercharging pressure control valve 57 normally closes the passage 56 and causes the pressure chamber 53 to have a compressor.
It is designed to guide the high pressure on the downstream side of the compressor 19.However, as will be described later, the passage 56 is opened and the upstream side of the compressor 19 is opened when the supercharging pressure is rapidly increased such as during rapid acceleration. The pressure (atmospheric pressure) is guided to the pressure chamber 53 via the throttle 58,
The pressure inside 53 is designed to be relatively low. When the pressure in the pressure chamber 53 relatively decreases in this way, the waste gate valve 43 becomes difficult to open, and the supercharging pressure increases.

Electronic control unit (ECU) 70 equipped with a microcomputer
Are formed on the engine body 10 from a rotation sensor 61 attached to a distributor (not shown), the engine speed Ne from the air flow meter 17, the intake air amount Q, from the throttle sensor 62 connected to the throttle valve 20 to the throttle opening THA. The cooling water temperature THW is input from the water temperature sensor 63 attached to the water jacket, the signal indicating the vehicle speed SPD is input from the vehicle speed sensor 64, and the ignition timing of the ignition timing is determined based on the signal obtained from the knock control sensor 65 attached to the engine body 10. The retard amount AK is determined, and the boost pressure control valve 57 is controlled based on these data.

The ECU 70 is a central processing unit (CPU) 71, a read-only memory (ROM) 72, a random access memory (RAM) 73, and another random storage element that is powered by an auxiliary power source and can retain memory even when the engine is stopped. It has an access memory (RAM) 74, an A / D converter 75, and a buffered input / output (I / O) port 76, which are interconnected by a bus 77. Air flow meter 17, throttle sensor 6
2, water temperature sensor 63, and knock control sensor 65
Output signal is input to the A / D converter 75, and the rotation speed sensor 61
The output signal of the vehicle speed sensor 64 is input to the I / O port 76. Based on these signals, the ECU 70 outputs a command signal to the supercharging pressure control valve 57 according to the flowchart shown in FIG.

The flowchart of FIG. 1 will be described.

In step 101, the engine speed Ne is 1400 rpm
If it is in the range of 4800 rpm, steps 102 and below are executed, but if it is outside this range, step 108 is executed.
In step 108, the supercharging pressure control valve 57 is turned off, that is, closed, and the compressor 19 is placed in the pressure chamber 53 of the actuator 50.
The waste gate valve 43 opens according to the pressure, that is, the supercharging pressure, and acts to suppress the supercharging pressure to a certain value or more. Therefore, the upper limit value of the supercharging pressure is set to a normal value.

When the affirmative decision is made in step 101, and the routine proceeds to step 102, it is decided whether or not the cooling water temperature THW is in the range of 70 ° C to 100 ° C. If it is outside this range, step 108 is executed, and if it is within this range Steps 104 and below are executed. In step 103, it is judged whether or not the throttle opening THA is larger than 60 ° C., and if it is smaller, step 108 is executed, and if it is larger, steps 104 and thereafter are executed. At step 104, it is judged if the vehicle speed is higher than 20 km / h. Vehicle speed is 20km / h
If it is below, step 108 is executed, and if it is larger than 20 km / h, step 105 is executed. In step 105, it is judged whether or not the retard amount AK of the ignition timing is smaller than 8 °. If it is larger, step 108 is executed, and if it is larger, step 106 is executed.
The following is done: If it is determined in step 106 that the ratio Q / N of the intake air amount to the engine speed is within the range of 0.6 l / rev 1.8 l / rev, step 107 is executed, and it is determined that it is outside the range. , Step 108 is executed.

If the determinations in steps 101 to 105 are affirmative, the engine combustion is normal and the engine speed has not risen sufficiently even though the throttle valve opening is relatively large.
It is determined that the engine is in rapid acceleration. Initially, engine load Q /
The determination in step 106 is affirmative because N is not so large, and in step 107, the boost pressure control valve 57 is turned on.
State, i.e. open, pressure chamber 53 of actuator 50
Then, the pressure (atmospheric pressure) on the upstream side of the compressor 19 is introduced through the throttle 58. As a result, the waste gate valve 43 becomes difficult to open, the upper limit value of the supercharging pressure is increased as compared with the normal time, and the supercharging pressure exceeds the upper limit value of the normal time and rises as shown in FIG. At this time, if the throttle valve opening THA is not so large as shown by the solid line, the engine load Q / N does not become abnormally large as shown by the solid line, and good acceleration performance is obtained without damaging the engine. Will be realized.

However, when the throttle valve opening THA is near full opening (90 °) as shown by the alternate long and short dash line, the intake air amount increases because the intake resistance in the intake passage is small even with the same boost pressure, and the engine load Q / N becomes abnormally large as shown by the chain line,
The engine may be damaged. Therefore, at this time, the determination in step 106 is denied and step 1
Going to 08, the upper limit of supercharging pressure is lowered to the normal size,
Prevent engine damage.

In addition, when the determination in step 106 is denied and the upper limit value of the supercharging pressure is lowered, it is not always necessary to lower it to a normal value.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the engine load from becoming too large during sudden acceleration, etc., and prevent the engine from being damaged.

[Brief description of drawings]

FIG. 1 is a flow chart of a control program according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an engine to which the embodiment of the present invention is applied. FIG. 3 is a time chart of the throttle valve opening, supercharging pressure, and engine load when the flow chart shown in FIG. 1 is executed. 18 …… Supercharger (turbocharger), 43 …… Wastegate valve, 70 …… Electronic control unit (ECU).

Claims (1)

[Claims] 1. The upper limit of boost pressure is set to a first set value except when the engine is accelerated, and the upper limit of boost pressure is set to the first set value when the engine is accelerated.
In a supercharging pressure control method for increasing a set value to a second set value, when the engine load exceeds a predetermined value during the engine acceleration, an upper limit value of the supercharging pressure may be decreased from the second set value. Characteristic supercharging pressure control method.