JPS62131922A - Supercharging pressure control method - Google Patents

Abstract

PURPOSE:To prevent an engine from damage, by relatively reducing the upper limit value of a supercharging pressure if the engine load exceeds a specified value, when the upper limit value of the supercharging pressure is set high. CONSTITUTION:The pressure chamber 53 of an actuator 50 which drives the waste gate valve 43 of a supercharger 18 is communicated to the down stream side of a compressor 19 through a passage 54, and at the same time, communicated to the upperstream side of the compressor 19 through a supercharging pressure control valve 57, and a throttle 58. An electronic control unit 70 receives various operating status detection signals to control the supercharging pressure control valve 57 on the basis of those signals. In case of the rapid acceleration, etc., the control valve 57 is turned on and opened to elevate the upper limit value of the supercharging pressure, however, when the engine load exceeds the specified value, the control valve 57 is turned of and closed, and the upper limit value of the supercharging pressure is reduced, Thus any engine damage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the boost pressure of an internal combustion engine equipped with a supercharger.

[Conventional technology and problems]

If the supercharging pressure becomes too high, it may cause damage to the engine, so conventionally, the upper limit value of the supercharging pressure is determined by a wastegate valve or the like. However, normally, the engine is operated at full load only for a relatively short period of time when the vehicle is being accelerated or overtaken, and even during this period, the upper limit of boost pressure is kept at the same value as during normal operation. If the vehicle is maintained at a constant value, sufficient acceleration performance of the vehicle will not be obtained.

Therefore, it has been proposed to set the upper limit value of the supercharging pressure relatively high only during a short period of time when full load operation is performed (Japanese Patent Application Laid-Open No. 157017/1983).

However, if the load on the engine increases too much during such transient high-load operation, there is a risk that the engine will be damaged, which poses a problem that must be prevented.

[Means for solving problems]

The boost pressure control method according to the present invention is configured to relatively lower the upper limit of boost pressure when the engine load exceeds a predetermined value while the upper limit of boost pressure is set high. It is a feature.

〔Example〕

The present invention will be explained 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.
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 boat 24 extending from the combustion chamber 13 and connected to the intake passage 14 is opened and closed by an intake valve 25.
An exhaust port 26 extending from the exhaust passage 15 and connected to the exhaust passage 15 is opened and closed by an exhaust valve 27.

The air cleaner 16 is provided at the most upstream side of the intake passage 14, and the air flow meter 17 is provided at the downstream side thereof.

A compressor 19 of the turbocharger 18 is provided further downstream, and a throttle valve 20 is provided downstream of the compressor 19. The throttle valve 20 changes the internal flow area of the intake passage 14 in conjunction with an accelerator pedal (not shown). A surge tank 21 is formed downstream of the throttle valve 20 in the intake passage 14 .

A turbine 41 of the turbocharger 18 is provided in the middle of the exhaust passage 15, and a bypass passage 42 that bypasses the turbine 41 is formed.

In the turbocharger 18, a turbine 41 is rotationally driven by the exhaust gas passing through the exhaust passage 15, which causes the compressor 19 to rotate and increase the pressure of the air taken in from the intake passage 14. The wastegate valve 43 opens and closes the bypass passage 42 to adjust the amount of exhaust gas supplied to the turbine 41 and
Controls the rotation of 8. The actuator 50 that opens and closes the wastegate valve 43 has a conventionally known configuration, and has a shell 51 partitioned by a diaphragm 52 to form a pressure chamber 53, and a passage 54 in the pressure chamber 53.
The pressure immediately downstream of the compressor 19 in the intake passage 14 is transmitted through the compressor 19 . When the pressure within the pressure chamber 53 overcomes the elastic force of the spring 55, the wastegate valve 43 opens the bypass passage 42, suppresses the exhaust gas passing through the turbine 41, and reduces the compressor flexor 19 of the turbocharger 18. Keep the outlet pressure constant.

A passage 56 that branches off from the middle of the passage 54 is connected to the intake passage 14.
This passage 56 communicates with the upstream side of the compressor 19.
A supercharging pressure control valve 57 and a throttle 58 are provided in the middle. The supercharging pressure control valve 57 normally closes the passage 56 and sends high pressure downstream of the compressor 19 to the pressure chamber 53, but as will be described later, the supercharging pressure may be reduced during sudden acceleration, etc. When increasing the pressure rapidly, the passage 56 is opened, and the pressure (atmospheric pressure) on the upstream side of the compressor 19 is guided to the pressure chamber 53 through the throttle 58, so that the pressure in the pressure chamber 53 is made relatively low. It has become. When the pressure within the pressure chamber 53 is relatively reduced in this manner, the wastegate valve 43 becomes difficult to open, and the supercharging pressure increases.

Electronic control unit (ECU) 7 equipped with a microcomputer
0 is the engine rotation speed Ne from the rotation speed sensor 61 attached to the distributor (not shown), the intake air amount Q from the air flow meter 17, and the throttle opening T)IA from the throttle sensor 62 connected to the throttle valve 20.
, the cooling water temperature THW from the water temperature sensor 63 attached to the water jacket formed in the engine body 10,
A signal indicating the vehicle speed SPD is inputted from the vehicle speed sensor 64, and the ignition timing retard 1i1AK is determined based on the signal obtained from the knock control sensor 65 attached to the engine body 10, and the supercharging is performed based on these data. Controls the pressure control valve 57.

ECtl 70 is a central processing unit (CPU) 71,
Read only memory (ROM) 72, random access memory (RAM) 73, another random access memory (RAM) 74 as a non-volatile storage element that can be supplied with power from the auxiliary power source and retain memory even when the engine is stopped, A/
D converter 75 and buffered output (I 10)
It has ports 76 and these are interconnected by a bus 77. Air flow meter 17, throttle sensor 62
, water temperature sensor 63, and knock control sensor 6
The output signals of the rotation speed sensor 61 and the vehicle speed sensor 64 are input to the I10 port 76. Based on these signals, the EC[I 70 outputs a command signal to the boost pressure control valve 57 according to the flowchart shown in FIG.

The flowchart in FIG. 1 will be explained.

In step 2 step 101, the engine speed Ne is 1
If it is within the range of 40 Orpm to 4,800 rpm, steps 102 and subsequent steps 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 pressure on the downstream side of the compressor 19 is guided to the pressure chamber 53 of the actuator 50, and the wastegate valve 43 controls the pressure.
In other words, the valve opens according to the boost pressure and acts to suppress the boost pressure above a certain value. Therefore, the upper limit value of the boost pressure is set to a normal value.

An affirmative determination is made in step 101, and step 102
When proceeding to step 10, it is determined whether the cooling water temperature THW is within the range of 70°C to 100°C, and if it is outside this range, step 10 is performed.
8 is executed, and if it is within this range, steps 104 and subsequent steps are executed. In step 103, the throttle opening TH
It is determined whether A is greater than 60°. If it is smaller, step 108 is executed; if it is larger, steps 104 and subsequent steps are executed. In step 104, the vehicle speed is 2Qkm/h.
It is determined whether or not the value is larger than that. If the vehicle speed is 20 km/h or less, step 108 is executed, and if it is greater than 2Q km/h, step 105 is executed. Step 10
In step 5, it is determined whether the ignition timing retard angle IAK is smaller than 8°. If it is, step 108 is executed, and if it is larger, steps 106 and subsequent steps are executed. Step 106
When the ratio Q/N of intake air amount and engine speed is 0,
61 /rev 1.81 /rev, step 107 is executed, and if it is determined that it is outside that range, step IO8 is executed.

If all of steps 101 to 106 are answered in the affirmative, the ECU 70 determines that the engine is currently rapidly accelerating and that it is necessary to increase the engine output.
Step 107 is executed. In step 107, the supercharging pressure control valve 57 is turned on, that is, opened, and the pressure (atmospheric pressure) on the upstream side of the compressor 19 is introduced into the pressure chamber 53 of the actuator 50 via the throttle 58. As a result, the waste gate valve 43 becomes difficult to open, and the supercharging pressure increases.

When step 107 is executed, the upper limit value of the boost pressure is set relatively high, and the engine output is increased.

On the other hand, when step 108 is executed, the upper limit value of the boost pressure is set to a normal level, that is, relatively low. Therefore, for example, when the engine load becomes excessive beyond a predetermined value, the boost pressure is suppressed and the load is reduced, thereby preventing damage to the engine.

Note that when it is determined in step 106 that the engine load is too large and the upper limit value of the boost pressure is lowered, it is not necessarily necessary to set the upper limit value during normal operation, and it is sufficient to simply lower the upper limit value at that time relatively. .

〔Effect of the invention〕

As described above, according to the present invention, the engine load does not become too large during sudden acceleration, etc., and damage to the engine can be prevented.

[Brief explanation of drawings]

FIG. 1 is a flowchart 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. 18...Supercharger (turbocharger), 43...Wastegate valve, 70...Electronic control unit (ECU).

Claims (1)

[Claims] 1. When the engine is operated under a transient high load, in a boost pressure control method that increases the upper limit of boost pressure than during normal operation, when the upper limit of boost pressure is set high, the engine A supercharging pressure control method characterized in that when the load on the supercharging pressure exceeds a predetermined value, the upper limit value of the supercharging pressure is relatively lowered.