JPH0563608B2 - - Google Patents

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. 29708, 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 the long intake system is used when the engine speed is low, and when the engine speed is high. 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 inertial supercharging of the intake air is performed. It can be done.
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. However, if such a setting is used, for example, even if the intake system is switched at the set rotation speed as the engine speed increases during acceleration, the set rotation speed will be exceeded due to a response delay in the control means and switching means. Actual switching of the intake system is performed even when the set rotational speed is reached, resulting in a decrease in engine output torque from the time when the set rotational speed is reached until the actual switching, and smooth acceleration operation cannot be expected.

To deal with this, it is conceivable to issue a switching command for the intake system in advance at an engine speed slightly before the set speed, but since the rate of increase in engine speed changes depending on the operating condition, the switching command described above may be issued. Even if you uniformly determine the engine speed that produces , you will not get a satisfactory result.

(Object of the Invention) The present invention focuses on the fact that the higher the gear reduction ratio of the transmission is used, the larger the load and the slower the increase in engine speed. In other words, by changing the engine speed that commands the intake passage shape to be changed,
The purpose is to prevent the engine output from decreasing due to the above switching by allowing the actual change in the shape of the intake passage to be made at a set rotational speed determined by allowing a delay in response in the actuator or the like.

(Structure of the Invention) In the present invention, the substantial shape of the intake passage (passage length and and control means for setting the engine rotation speed at which a shape change command is issued to the shape change means to be lower as the reduction ratio of the transmission used is larger.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In the engine intake system shown in FIG.
3 is a cylinder head into which the piston 2 is inserted; 3 is a cylinder head in which an intake port 4 and an exhaust port 5 are formed; 6 is an intake valve that opens and closes the intake port 4; 7 is an exhaust valve that opens and closes the exhaust port 5;
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 communicate the surge tank 9 and the intake port 4. A fuel injection valve 12 is provided in the short intake passage 1.
1 is interposed with an on-off valve 13 that opens and closes the passage.

In the case of 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 port 4 and the long intake passage 10 are opened to the surge tank 9. Due to the inertia effect between the intake passage and the intake passage, the engine rotation speed at which the natural frequency of the intake passage is synchronized appears in the high rotation range, and when the on-off valve 13 is open, the surge in the intake port 4 and the short intake passage 11 is suppressed. The inertial effect between the tank 9 and the opening becomes significant, and the engine rotational speed at which the natural frequency of the intake passage is synchronized appears in the low rotational speed range. That is, when the long intake passage 10 is used, the negative pressure wave generated by the downward movement of the piston 2 is reversed with the opening on the side of the long intake passage 10 as an open end, and returns to the intake port 4 as a positive pressure wave. Therefore, the pressure in front of the intake valve 6 becomes a composite pressure of this positive pressure wave and 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 valve 6 is closed, that is, When the natural frequency of the intake passage and the engine speed are synchronized, the intake air filling efficiency becomes high and the engine output torque peaks, but this long intake passage 10
The length of is set so that the synchronized engine speed Nl is expressed 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.

Therefore, an actuator 14 is attached to the opening/closing valve 13 to perform its opening/closing operation, and
A control means 15 is connected to this actuator 14, and this control means 15 has a rotation sensor 16 that detects the engine speed n, and a reduction ratio of the transmission, that is, a shift position S _i of the speed change lever (speed change gear). The actuator 14 receives a detection signal from a shift position sensor 17 and outputs an opening/closing switching signal to the actuator 14 when the engine speed corresponds to the reduction ratio.

That is, the control means 15 includes a memory storing the engine speed for switching between opening and closing corresponding to the shift position S _i , a setting means for reading and setting the corresponding engine speed N _si from the memory based on the shift position signal, and a rotation sensor 16 . a determination means for determining whether or not the engine rotation speed n detected at is greater than the set engine rotation speed _Nsi ; and a valve opening signal when the engine rotation speed n detected in response to this determination is large. and an output means for outputting a valve closing signal when the valve is not in use. The engine speed N _si stored in the memory is
As the shift position decreases from 3rd gear to 2nd gear to 1st gear, that is, as the reduction ratio increases, the rotation speed becomes lower. Specifically, the engine rotation speed N _p at a position corresponding to the intersection of the torque characteristic line when using the long intake passage 10 and the torque characteristic line when using the short intake passage 11 shown in FIG. It is determined by the product of the engine speed increase rate at the shift position S _i used during high load operation (during acceleration operation) and the response delay time from the signal output by the control means 15 until the on-off valve 13 actually opens. An engine rotational speed _Nsi obtained by subtracting the rotational speed from the engine rotational speed _Np is stored in correspondence with each shift position.

The flow of processing in this control means 15 is shown in FIG. 3, in which the engine speed n is read from the rotation sensor 16 and the shift position S _i is detected from the shift position sensor 17 (steps). ,
The engine rotational speed Nsi at which opening and closing of the on-off valve 13 should be switched is read from the memory according to the shift position Si (step). Then, based on the judgment as to whether or not the engine speed n is larger than the engine speed Nsi for switching, if YES, a signal to open the on-off valve 13 is output, and if NO, a signal to close it is output. Output (step,,
).

Therefore, in the above-mentioned embodiment, first, when the engine speed n is low, the on-off valve 13 is closed, and supercharging is performed using the inertia effect of the intake air in the long intake passage 10. During acceleration operation (high load operation), when the engine speed Nsi corresponds to the transmission shift position Si at that time,
A valve opening signal is output from the control means 15 to the actuator 14, and the opening/closing valve 13 is activated at the time when the engine speed is No, that is, when the inertial supercharging effect in the short intake passage 11 is greater than the inertial supercharging effect in the long intake passage 10. The valve becomes open when the value becomes larger. As a result, the long intake passage 10 and the short intake passage 1 can be connected to each other without causing a temporary decrease in output torque due to switching of the on-off valve 13.
The inertial supercharging effect in each of the above steps can be efficiently utilized to accelerate the engine.

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. 4, one cylinder has two intake ports 21, 22 separated by a partition wall 20, and both intake ports 21, 22 are separated by a partition wall 20.
22 and the surge tank 23 is partitioned halfway into a first and second intake passage 25, 26 by a partition wall 24 extending from the surge tank 23, and both intake passages 25, 26 are connected to the partition wall 24. 24, and a fuel injection valve 27 is provided at this junction. The second intake passage 26 is provided with an on-off valve 28 that opens and closes the passage.

The first intake passage 25 introduces intake air into the cylinders throughout the engine speed range, and the second intake passage 26 introduces intake air by opening the on-off valve 28 only in the high engine speed range. There is. Therefore, when the on-off valve 28 is in the closed state, the cross-sectional area of the intake passage is narrowed by the amount that the second intake passage 26 is closed, and the natural frequency of the intake passage is adjusted to the engine rotation speed in the low rotation range. When the on-off valve 28 is in the open state, the cross-sectional area of the intake passage becomes larger than the sum of the first and second intake passages 25 and 26. The natural frequency is synchronized with the engine speed in the high speed range, and an inertial supercharging effect of the intake air is produced.

In this embodiment of changing the cross-sectional area of the passage, as in the previous embodiment, a reduction in engine output torque is prevented by outputting a switching signal for the on-off valve 28 even at the engine speed corresponding to the shift position of the transmission. can be achieved.

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. The on-off valve may be opened to increase the engine output.

(Effects of the Invention) According to the present invention, as the reduction ratio used by the transmission increases, the setting of the engine rotation speed for outputting a change signal to the intake passage shape changing means is shifted to the lower rotation side. It is now possible to prevent a drop in the output torque when changing the characteristics of the intake inertia supercharging effect, regardless of the change in the rising speed and the response delay of the above-mentioned changing means.
The acceleration performance of the engine can be improved.

[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. 4 are configuration diagrams showing an intake passage shape changing means in another embodiment. 4, 21, 22... Intake port, 6... Intake valve, 9, 23... Surge tank, 10... Long intake passage, 11... Short intake passage, 13, 28... Open/close valve, 15... Control Means, 16... rotation sensor,
17...Shift position sensor, 25...First intake passage, 26...Second intake passage.

Claims (1)

[Claims] 1. Intake passage shape changing means that changes the substantial shape of the intake passage and synchronizes the natural frequency of the intake passage with the engine rotation speed in different rotation ranges to obtain an intake inertial supercharging effect. An intake device for an engine, characterized in that the engine is equipped with a control means that sets the engine rotation speed at which a shape change signal is output to the shape change means to a lower speed as a reduction ratio used by the transmission increases.