JPS6223533A - Supercharger abnormality detecting method - Google Patents

Abstract

PURPOSE:To make it possible to detect quickly the abnormality in supercharging pressure in ordinary operation in which the maximum supercharging pressure is relatively low by varying reference value for judging the supercharging pressure to be abnormal according to the variety of the maximum supercharging pressure. CONSTITUTION:Sucked air amount, engine speed, and engine acceleration signals are input respectively from an air flow meter 17, revolution detector 37, and the throttle sensor of a throttle valve 21 to an ECU 50. The supercharging pressure during acceleration is regulated below the first upper limit A1 of Q/N and rises as a curved line shown in a solid line P. If the supercharging pressure rises above the upper limit value A1, fuel supply stops. The supercharging pressure in ordinary operation is regulated below the second upper limit value A2 of Q/N.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting an abnormal increase in supercharging pressure in a supercharged engine.

[Conventional technology and problems]

In order to prevent engine damage due to excessive boost pressure, boost pressure is normally limited to no more than a certain value.If boost pressure rises abnormally despite this, The fuel supply is cut off, thereby protecting the engine. When detecting such boost pressure abnormalities, the reference value for determining whether or not there is an abnormality is set to a value slightly higher than the maximum boost pressure, for example, 110 mmHg, so that abnormalities can be detected more quickly. It looks like this. However, in the case of an engine that increases the maximum boost pressure during acceleration (Japanese Unexamined Patent Publication No. 146023/1983), the above reference value has conventionally been set to a value slightly higher than the larger maximum boost pressure. However, when the maximum boost pressure is relatively low, that is, during normal operation, the reference value is too high, causing the problem that abnormality in the boost pressure cannot be detected early.

[Means for solving problems]

The supercharger abnormality detection method according to the present invention is characterized in that a reference value for determining whether the magnitude of supercharging pressure is abnormal is changed in accordance with the maximum supercharging pressure.

〔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.

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.

Further downstream, a compressor 19 of the turbocharger 18 is arranged. The throttle valve 21 is the compressor 1
It is provided on the downstream side of the air intake passage 9 and changes the flow area in the intake passage 14 in conjunction with an accelerator pedal (not shown). The fuel injection valve 22 is provided in the intake passage 14 further downstream than the throttle valve 21 and near the combustion chamber 13 .

A turbine 25 of the turbocharger 18 is provided in the middle of the exhaust passage 15, and a bypass passage 26 that bypasses the turbine 25 is formed.

In the turbocharger 18 , a turbine 25 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 27 opens and closes the bypass passage 26 to adjust the amount of exhaust gas supplied to the turbine 25 and
Controls the rotation of 8. The actuator 28 that opens and closes the waste gate valve 27 has a conventionally known configuration, and the inside of the cowl 29 is partitioned by a diaphragm 30 to form a pressure chamber 31 and an atmospheric chamber 32. 33 are provided. On the other hand, the pressure immediately downstream of the compressor 19 in the intake passage 14 is transmitted into the pressure chamber 31 via the passage 34 . However,
When the pressure in the pressure chamber 31 overcomes the elastic force of the spring 33, the wastegate valve 27 opens the bypass passage 26, controls the exhaust gas passing through the turbine 25, and adjusts the outlet pressure of the compressor 19 of the turbocharger 18. Keep the pressure constant.

The end of a passage 35 that branches off from the middle of the passage 34 is open to the atmosphere, and a switching valve 36 provided in the middle of this branch passage 35 is switched and controlled by an electronic control unit (ECU) 50 to open the passage 35. Open and close. The switching valve 36 is connected to the passage 35
When the actuator 28 opens, the pressure chamber 31 of the actuator 28 communicates with the atmosphere through the passage 35, and when the switching valve 36 closes the passage 35, the pressure chamber 31 communicates only with the passage 34. Therefore, when the switching valve 36 is opened to lower the pressure in the pressure chamber 31, the wastegate valve 27 becomes difficult to open, thereby increasing the maximum boost pressure.

As will be described later, the ECU 50 controls the switching valve 36 to change the maximum boost pressure according to the engine operating conditions,
It also controls the fuel injection valve 22. Therefore, the ECU 3O receives a signal indicating the amount of intake air from the air flow meter 17,
A signal indicating the engine rotation speed is input from the rotation speed detector 37, and a signal indicating whether the engine is in an acceleration state is input from the throttle sensor connected to the throttle valve 21.

FIGS. 1(a) and 1(b) show flowcharts of control performed by the ECU 50. FIG. 1 (The program for controlling al is interrupted every 30° crank angle, for example, and the acceleration state of the engine is first detected in step 101, and then the acceleration state (for example, the opening speed of the throttle valve 21) is detected in step 102. is larger than a certain value.If an affirmative determination is made in step 102, step 103 is executed, and the switching valve 3
A command signal YTPC is set to open 6. On the other hand, if a negative determination is made in step 102, step 104 is executed, and the command signal YTPC is reset to close the switching valve 36. Setting YTPC means opening the waste gate valve 27 and increasing the maximum boost pressure.

In step 105, it is determined whether YTPC has been set, that is, whether the maximum boost pressure has been increased. If an affirmative determination is made here, the process moves to step 106 and after clearing the counter CTPC, step 107 is executed and Q/N (Q is the intake air amount, N is the engine speed) is set to the first upper limit value AI ( For example 1,842 /rev
) or more. Counter CTPC is ECU
50, and counts up every 32 milliseconds, for example. That is, the counter CTPC is cleared every time YTPC is set, and starts measuring time after YTPC is reset.

Now, in step 107, Q/N is determined to be the first upper limit value A.
If it is 8 or more, it is determined that the supercharging pressure is abnormal, and the process moves to step 108, where a supercharging pressure abnormality flag XFCQN is set. On the other hand, if Q/N is smaller than the first upper limit value A in step 107, the process moves to step 111.

Here, Q/N is the return value B (for example, 1.0 to 1.212
/rev) or more, and if the determination is affirmative, the process moves to step 112 and the flag XFCQN is reset.
Conversely, if the determination is negative, step 112 is skipped and the program ends.

On the other hand, if a negative determination is made in step 105, that is, if the engine is not in an acceleration state and the maximum boost pressure is relatively low, step 109 is executed and the counter C
It is determined whether TPC is equal to or greater than a (for example, 0.5 to 2 seconds). That is, it is determined whether or not more than a time has elapsed since the counter CTPC was cleared in step 106 the last time this program was executed. If at least a has elapsed, step 110 is executed, and if at least a has not elapsed, step 107 is executed.

FIG. 1(b) is a program that is processed after the program in FIG. 1(al) is executed. Step 201
Then, it is determined whether the flag XFCQN is set. If XFCQN is reset, this program is terminated by skipping step 202 to interrupt fuel injection, and if XFQN is reset, injector 2 is reset.
2, execute step 202 and end this program.

Figure 3 shows the control signal YTPC,
It shows the upper limit value AI+A2 of Q/N and the change in boost pressure. At time t1, when YTPC is set because the acceleration state has become larger than a certain value, the boost pressure is regulated to the first upper limit A1 of Q/H, and the maximum boost pressure is enhanced. As a result, the supercharging pressure increases as shown by the solid line P. When the boost pressure starts to rise in this way, the program in FIG.
1,102,103゜105, 106.107.111
Meanwhile, XFCQN is reset in the initial setting at the start of this control, and the program shown in FIG. 1 (bl) is executed in the order of steps 201 and 202, and the injection valve 22 injects fuel.

After time t2, if the boost pressure exceeds the maximum boost pressure, in other words, if Q/N exceeds the first upper limit value A1, then in the program shown in FIG.
07 to step 108, XFCQN is set, and step 202 in the program of FIG. 1(b)
is skipped and the fuel supply is cut off. After that, for example, when the throttle valve 21 is closed and Q/N becomes small, and a negative determination is made in step 107, step 111
Then, it is determined whether Q/N is equal to or greater than the return value B. That is, if the Q/N has not decreased to the return value B, step 112 is skipped and XFCQN is kept set to maintain fuel supply cutoff, but if the Q/N has decreased below the return value B, the process proceeds to step 112. Move to reset XFCQN and restart fuel supply.

Now, referring again to FIG. 3, when the acceleration state changes at time t2 and YTPC is reset, the program in FIG.
, 109, and if the value of the counter CTPC has not reached a, step 107 is executed. In other words, by resetting VT p c, the maximum boost pressure is lowered and the actual boost pressure starts to decrease as shown by the solid line P, but by executing step 107, Q/N is lowered to the first upper limit. The limit by value A1 is maintained. If the value of the counter CTPC is equal to or greater than a in step 109, the process moves to step 110, and Q/N falls to the second upper limit value A2. That is, Q/N is limited by the second upper limit value A2 for the first time at time t3, and therefore, even if the boost pressure is higher than the second limit value A2 between times t2 and t3, the This eliminates the possibility of incorrectly detecting that the supply pressure is abnormal.

As described above, according to the above embodiment, the upper limit value of Q/N, that is, the reference value for determining whether the boost pressure is abnormal, changes depending on the magnitude of the maximum boost pressure. Abnormalities in boost pressure can be detected quickly during normal operation when boost pressure is relatively low. In addition, when the maximum boost pressure becomes low, the upper limit of Q/N will be lowered after a predetermined period of time has passed, so even if it takes time for the boost pressure to decrease, abnormalities in the boost pressure will not be detected. There is no risk of false detection.

Note that the present invention is applicable not only to turbochargers but also to mechanical superchargers.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to quickly detect an abnormality in boost pressure during normal operation where the maximum boost pressure is relatively low.

[Brief explanation of the drawing]

FIG. 1fa) is a flowchart of a control program according to an embodiment of the present invention, FIG. 1(bl) is a flowchart of a program for cutting off fuel supply, and FIG. Fig. 3 is a graph showing temporal changes in the reference value for determining whether the supercharging pressure is abnormal and the supercharging pressure. 18...Supercharger.

Claims (1)

[Claims] 1. A supercharger in which the maximum boost pressure can be changed according to the operating condition of the engine, wherein the maximum boost pressure is set to a reference value for determining that the magnitude of the boost pressure is abnormal. A method for detecting an abnormality in a supercharger, characterized by changing the pressure in accordance with the supply pressure. 2. When switching from a relatively high maximum boost pressure to a low maximum boost pressure, the reference value is changed after a predetermined period of time has passed since the switch. Anomaly detection method.