JPS61106917A - Intake-air device in engine - Google Patents

Abstract

PURPOSE:To provide an engine output lowering system having less shock, in an engine incorporating two intake-air passages having different pipe lengths for each cylinder, by changing over the intake air passage from one to another intake-air passage which has a less inertia supercharge effect upon abnormal engine operation. CONSTITUTION:Intake-air passages 10, 11 having long and short lengths measured from an intake-air manifold 9 are communicated to an intake valve 6 of an engine 1, and a shut-off valve 13 which opens upon high speed operation of the engine is disposed in the short intake-air passage 11. A control means 15 controls the drive of the shut-off valve 13 in accordance with outputs from a rotational speed sensor 17, a cylinder wall temperature sensor 17, an exhaust gas temperature sensor 19 and a catalyst temperature sensor 21. When any abnormality such as, for example, an excessive rotational speed of the engine, an excessive rise in the temperature of exhaust gas, etc. due to excessive output power of the engine, is detected by any one of the sensors, the control means 15 reversely operates the opening and closing of the shut-off valve 13 to lower the output power of the engine.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an engine intake system.

(Prior art) Regarding the intake system of an engine, for example,
As described in Publication No. 70r, two intake systems are provided, one with a long intake passage and one with a short intake passage from the intake port to the surge tank, and when the engine speed is low, the long intake system is used, and when the engine speed is high, the intake system is Techniques for switching the intake system to use a shorter intake system are generally known.

In the case of this conventional technology, by switching the intake system between long and short positions, the natural frequency of the intake system is synchronized with the engine speed at two points, one where the engine speed is low and one where the engine speed is high, and the intake air is inertial supercharged. will be carried out.

The engine speed at which the intake system is switched is generally the engine speed (engine speed N in Figure 2) at which the inertial supercharging effect is greater with a short intake system than with a long intake system. It is set.

Incidentally, engine output may temporarily increase due to changes in operating conditions or environment, leading to overheating, overspeeding, abnormal increase in combustion pressure, etc., which may adversely affect durability.

Conventionally, attempts have been made to temporarily reduce the output of the engine through spark cuts and fuel cuts, but spark cuts cause unburned gas to be discharged, and fuel cuts also reduce the output of the engine. There is a problem in that the possibility of misfire increases and unburned gas is easily discharged, and the exhaust gas temperature and exhaust gas purification catalyst temperature rise abnormally, resulting in poor exhaust gas purification.

(Purpose of the Invention) The present invention uses an intake inertia effect as a method for reducing output when an abnormality due to engine overpower is observed, instead of using conventional methods for reducing output that cause a large shock to the engine, such as spark cut or fuel cut. The aim is to provide a system that uses relatively small shocks to prevent abnormalities from occurring in the exhaust system.

(Structure of the Invention) In the present invention, the substantial shape of the intake passage ( means for changing the intake passage length and cross-sectional area), means for detecting an abnormality due to engine overpower, and when this abnormality is detected, the above-mentioned changing means changes the substantial shape of the intake passage according to the engine rotation at that time. and control means for changing the number of inertial supercharging effects to a smaller one.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In the engine intake system shown in FIG. 1, 1 is a cylinder into which a piston 2 is fitted, 3 is a cylinder head in which an intake boat 4 and an exhaust port 5 are formed, 6 is an intake pulp that opens and closes the intake boat 4, and 7 8 is an exhaust valve that opens and closes the exhaust port 5, and 8 is an intake manifold connected to the cylinder head 3. The intake manifold 8 includes a long intake passage 10 with a long passage length and a short intake passage 11 with a short passage length, which communicates the surge tank 9 and the intake boat 4.
A fuel injection valve 12 is installed at the downstream confluence of both intake passages 10.11.
Further, an on-off valve 13 for opening and closing the short intake passage 11 is interposed in the short intake passage 11.

In this example, the on-off valve 13 serves as a changing means for changing the substantial shape of the intake passage, and when the on-off valve 13 is closed, the intake boat 4 and the long intake passage 10 are connected to the surge tank 9. Due to the inertial effect between the intake passage and the opening, the engine rotation speed at which the natural frequency of the intake passage is synchronized is in a low rotation range, and when the on-off valve 13 is open, the intake boat 4
The inertia effect between the short intake passage 11 and the opening of the surge tank 9 becomes significant, and the engine rotation speed at which the natural frequency of the intake passage is synchronized is in a high rotation range. That is, when the long intake passage 1'0 is used, the piston 2
The negative pressure wave generated by the downward movement is reversed with the opening on the long intake passage 10 side as an open end, and returns to the intake boat 4 as a positive pressure wave. Therefore, the pressure in front of the intake pulp 6 is a composite pressure of the positive pressure wave and the negative pressure wave, and when the timing when the pressure before the valve and the cylinder pressure become the same pressure coincides with the timing when the intake pulp 6 is closed, In other words, when the natural frequency of the intake passage and the engine speed are synchronized, the intake air filling efficiency increases and the engine output torque peaks.
The length of this long intake passage 10 is set so that the synchronized engine speed N° C. appears in the low speed range, as shown in FIG. On the other hand, when the short intake passage 11 is used, the negative pressure wave is reversed with the opening on the short intake passage 11 side as the open end, but at this time the engine rotational speed Nh at which the natural frequency of the intake passage is synchronized is high. The length of this short intake passage 11 is set so that it appears in the area.

An actuator 14 is attached to the on-off valve 13, and a control means 15 is connected to the actuator 14. The control means 15 operates based on the engine rotation speed and the detection of an abnormality caused by engine overpower. A control signal is output to the actuator 14 to control opening and closing of the on-off valve 13. That is, in the case of this example, a rotation sensor 17 detects the engine rotation speed from the rotation of a rotating body 16 connected to the crankshaft, a wall temperature sensor 18 detects the wall temperature of the cylinder 1, and a wall temperature sensor 18 detects the temperature of exhaust gas. An exhaust temperature sensor 19 and a catalyst temperature sensor 21 that detects the temperature of a catalytic converter 20 that purifies exhaust gas each output detection signals to the control means 15.

The control means 15 controls the engine rotation speed n detected by the rotation sensor 17 to be higher than that in the short intake passage 10 than in the long intake passage 10.
The rotation speed N(
Means for determining whether the engine speed at the intersection point of the two torque characteristic lines in FIG. No, wall temperature sensor 18, exhaust temperature sensor 19
and whether or not the respective detected temperatures from the catalyst temperature sensor 21 have become abnormal values exceeding the respective set values. A method for determining whether or not an accompanying abnormality has been detected, and, if an abnormality is detected, for changing the substantial shape of the intake passage in such a way that the intake inertial supercharging effect at the engine speed n at that time is reduced. The actuator 14 of the on-off valve 13 is provided with means for outputting an open/close signal to the actuator 14 of the on-off valve 13.

The flow of processing in this control means 15 is shown in FIG. Determine whether or not the rotation speed exceeds the set rotation speed N at which the on-off valve 13 is switched between opening and closing (steps ■, ■).
. Next, if this judgment is YES, in step ■, N
In the case of O, an abnormality due to engine overpower is detected in any of the seven sensors listed above in step 10.
otherwise, a valve open signal (short intake passage 11 is used) is output. On the other hand, if the judgment in step (2) is that there is an abnormality, a valve open signal is output, and if there is abnormal heat, a valve close signal is output (steps (2), (3)).

Therefore, in the above embodiment, if there is no abnormality due to engine overpower, the on-off valve 16 is closed in the engine speed range where the engine speed n is low, and the long intake passage 10 is closed.
Supercharging is performed using the inertial effect of intake air. Then, when the engine speed n reaches a value equal to or higher than the set rotation speed N, the on-off valve 16 opens and moves, and supercharging is performed using the inertial effect of the intake air in the short intake passage 11.

However, when the engine speed n is in a high speed range, if an abnormality associated with engine overpower such as engine overspeed or abnormal rise in exhaust gas temperature is detected, the on-off valve 13 is closed and the intake passage is closed. The substantially longer side (long intake passage 1)
0). In this high rotation range, as shown in Fig. 2, there is almost no inertia supercharging effect of the intake air by the long intake passage 10, and the output torque of the engine decreases compared to when the short intake passage 11 is used, which eliminates the above abnormality. When the abnormality is resolved, the shape of the intake passage returns to the short intake passage 11 side again. This reduction in engine output torque is achieved by temporarily lowering the intake air filling efficiency, and does not cause large shocks such as engine misfires, and does not cause deterioration of the exhaust gas condition. On the other hand, when the engine speed n is in the low speed range, if an abnormality due to engine overpower (no overspeed of the engine) is detected, the on-off valve 13 opens.
The intake inertia effect in the short intake passage 11 acts to reduce the inertia supercharging effect in the long intake passage 10, reducing the output torque of the engine and eliminating the above abnormality.

Regarding the change in the substantial shape of the intake passage, in the above embodiment the length of the passage is changed, but the cross-sectional area of the passage may be changed as shown in FIG. That is, in the embodiment shown in FIG. 7, there are two intake ports 23 and 24 separated by the partition wall 22 for seven cylinders, and an intake port that communicates between both intake boats 26 and the surge tank 25. The passage is partitioned halfway into first and second intake passages 27, 28 by a partition wall 26 extending from the surge tank 25, and both intake passages 27, 28 merge before reaching the partition wall 26, and this merging A fuel injection valve 29 is provided in the section. The second intake passage 28 is provided with an on-off valve 60 that opens and closes the passage.

The first intake passage 27 introduces intake air into the cylinders throughout the engine speed range, and the second intake passage 28 introduces intake air by opening the on-off valve 60 only in the high engine speed range. being done. Therefore, when the on-off valve 30 is in the closed state, the cross-sectional area of the intake passage is narrow by the amount that the second intake passage 28 is closed, and the natural frequency of the intake passage is tuned to the engine speed in the low rotation range. When the on-off valve 30 is in the open state, the cross-sectional area of the intake passage is larger than the sum of the first and second intake passages 27 and 28. The natural frequency of the engine synchronizes with the engine speed in the high speed range, and an inertial supercharging effect of the intake air is produced.

Also in this embodiment of changing the cross-sectional area of the passage, as in the previous embodiment, it is possible to detect an abnormality due to excessive engine output and switch the opening/closing of the on-off valve 30 to reduce the output torque.

In the above embodiment, the substantial shape of the intake passage is changed according to the engine speed regardless of the level of the engine load. It is also possible to increase the output of the engine by opening the on-off valve under conditions of high load when the engine is not running.

□ (Effects of the Invention) According to the present invention, when there is an abnormality due to excessive engine output, the substantial shape of the intake passage is changed so that the intake inertia supercharging effect is reduced in order to reduce the output torque. Because of this, the engine receives less shock compared to conventional output reduction methods such as spark cutting, and prevents engine overheating and overspeeding without causing secondary harm associated with output reduction, such as deterioration of exhaust gas properties. This makes it possible to improve engine durability and effectively limit vehicle speed.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and FIG. 1 is a configuration diagram showing an example of an engine intake system, FIG. 2 is an output torque characteristic diagram, and FIG. 3 is a flowchart showing the flow of processing by the control means. Figures 1 and 2 are configuration diagrams showing intake passage shape changing means in another embodiment. 4.23.24 Old... Intake port, 6... Intake pulp, 9.25... Surge tank, 1o...
...Long intake passage, 11...Short intake passage,
13.30・Old・・Open □Valve closed, 15・・・・・
Control means, 17. Old rotation sensor, 18...
Wall temperature sensor, 19...Exhaust temperature sensor, 21...
...Catalyst temperature sensor, 27...7th intake passage, 28...2nd intake passage

Claims (1)

[Claims] (1) Means for changing the shape of the intake passage by changing the substantial shape of the intake passage and synchronizing the natural frequency of the intake passage with the engine speed in different rotation ranges to obtain an inertial supercharging effect on the intake air In the engine, the engine has an abnormality detecting means for detecting an abnormality due to excessive output of the engine, and the shape changing means is controlled in response to the abnormality detected by the abnormality detecting means, and the substantial shape of the intake passage is changed according to the engine rotation at that time. and control means for changing the inertial supercharging effect to a smaller one.