JPH0563609B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention comprises an intake passage consisting of a high-load intake passage and a low-load intake passage, and the high-load intake passage is provided with a shirt that closes when the load is low. This invention relates to an improvement in an engine intake system in which a timing valve is provided in the low-load intake passage, and the filling amount is controlled by closing the timing valve earlier than the closing timing of the intake port in the low-load range. It is something.

(Prior art) Conventionally, in the case of an engine in which the intake air filling amount is controlled by adjusting the opening degree of the throttle valve, there is a pumping loss due to throttling resistance, especially in the low load range, which improves the fuel efficiency of the engine. This has become a major obstacle. As an engine that reduces this pumping loss, a timing valve is provided in the intake passage near the intake port that is opened and closed at a predetermined timing, and the opening and closing timing of the timing valve is adjusted according to the operating state of the engine.
An engine has been proposed in which the intake air filling amount is controlled by the length of the opening period of the intake port and the timing valve, and the intake throttling resistance is eliminated to reduce pumping loss and improve fuel efficiency (for example, , see Japanese Patent Publication No. 58-23245).

In addition, in the above-mentioned prior example, the intake passage is configured into a high-load passage and a low-load passage, and the low-load passage is equipped with the timing valve, while the high-load passage is equipped with a shutter that closes when the load is low. The valve is installed to reduce pumping loss in the low load range, and the timing valve is made smaller to improve its reliability.Furthermore, the intake passage for low loads is suitable for generating swirl. The passage structure allows for improved combustibility.

Therefore, in an engine equipped with a timing valve and a shutter valve as described above, when the air-fuel ratio is shifted to lean in a specific operating range where the required output is low to improve fuel efficiency, the operating state For example, when the air-fuel ratio changes from a cold state to a warm state and the air-fuel ratio shifts to a lean state, or when the air-fuel ratio shifts to a rich state due to other conditions, if the charging amount is constant, sudden changes occur. Torque shock occurs due to a sudden decrease or increase in output.

Therefore, for example, when the air-fuel ratio shifts to lean, control has been carried out to increase the filling amount, but if this increase in filling amount is obtained by opening the shutter valve, the timing valve This will impair the pumping loss reduction effect achieved by the arrangement.

In other words, the pumping loss reduction effect of the engine described above is obtained by closing the timing valve and stopping the intake air supply in the latter half of the period when the intake port is open at low load, and by opening the shutter valve at this time. This is undesirable because it impairs this pumping loss reduction effect.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention provides a method for controlling the operation of a timing valve provided in a low-load intake passage and a shutter valve provided in a high-load intake passage according to the operating state. It is an object of the present invention to provide an intake system for an engine that reduces torque shock when changing the air-fuel ratio at low load while maintaining a loss reduction effect.

(Structure of the Invention) The intake device of the present invention has an intake passage composed of a high-load intake passage and a low-load intake passage, and the high-load intake passage is provided with a shutter valve that closes when the load is low. In an engine in which a timing valve is provided in the low-load intake passage and the timing valve closes at a time earlier than the intake port closes at a low load, when changing the air-fuel ratio at a low load,
The present invention is characterized in that it includes a controller that corrects the filling amount in a direction that reduces torque fluctuations caused by changing the air-fuel ratio by controlling the timing of the timing valve.

(Effects of the Invention) According to the present invention, when the air-fuel ratio is changed to lean or rich due to fluctuations in engine operating conditions at low load, the timing valve timing is changed at the same time as the air-fuel ratio is changed. By controlling and correcting the filling amount, it is possible to suppress the increase or decrease in output due to changes in the air-fuel ratio by increasing or decreasing the filling amount, reduce the occurrence of torque shock, and obtain good operating conditions. . Furthermore, by correcting the filling amount through timing control of the timing valve, the torque shock can be improved without impairing the pumping loss reduction effect achieved by installing the timing valve.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an engine equipped with an intake system of the present invention.

An intake port 7 that is opened and closed by an intake valve 6 and an exhaust valve 8 that opens and closes a combustion chamber 5 formed above a piston 4 between a cylinder head 2 and a cylinder block 3 of each cylinder of the engine body 1. The exhaust ports 9 are opened.

The intake passage 10 that communicates with the intake port 7 and supplies intake air includes an air cleaner 11 from the upstream side, an intake air amount sensor 12 that detects the amount of intake air, and a surge tank 13, and is connected to each cylinder from the downstream side of the surge tank 13. The intake passage 10a is bifurcated and is composed of a high-load intake passage 10a having a large passage area and a low-load intake passage 10b having a narrow passage area and formed for swirl generation. Furthermore, a fuel injection nozzle 16 for injecting fuel is arranged in the high-load intake passage 10a of each cylinder.

A shutter valve 17 is interposed in the middle of the high-load intake passage 10a, while a timing valve 18 is interposed in the middle of the low-load intake passage 10b.

The timing valve 18 is formed into a cylindrical shape that is driven to rotate in synchronization with the rotation of the engine, and is formed with an opening 18a that opens and closes the low-load intake passage 10b. The internal space of this timing valve 18 communicates with openings 18a for other cylinders of the multi-cylinder engine, and when the opening 18a of one cylinder is in an open state communicating with the downstream low-load intake passage 10b, The internal space is communicated with the upstream low-load intake passage 10b through the opening 18a of another cylinder, and is supplied with intake air.

On the other hand, the phase of the timing valve 18 with respect to the crank angle, that is, the opening/closing timing with respect to the intake port 7 is configured to be variable by a timing control means 19. Further, the opening degree of the shutter valve 17 is adjusted by an opening degree control means 20.

A control signal from the controller 21 is outputted to the timing control means 19 and the opening control means 20, which control the operation of the timing valve 18 and shutter valve 17 according to the operating state. In addition, the controller 2
1 outputs a fuel injection signal to the fuel injection nozzle 16 to control the fuel injection amount and injection timing, and also outputs a control signal to the on-off valve 23 of the bleed air passage 22 to perform bleed in accordance with the fuel injection timing. It controls the supply of air.

The controller 21 receives a signal from the intake air amount sensor 12 as a signal for detecting the operating state of the engine.
, a crank angle signal (engine rotation speed signal) from the crank angle sensor 24 , an accelerator signal from the accelerator sensor 25 , an intake pressure signal from the boost sensor 26 , and a water temperature sensor 2
The cooling water temperature signal etc. from 7 are input.

The basic control of the opening/closing timing of the timing valve 18 and the opening degree of the shutter valve 17 is based on the load condition corresponding to the amount of accelerator operation, etc., and closes the shutter valve 17 when the load is low, and closes the shutter valve 17 when the load exceeds a predetermined load. The valve opens according to the load. On the other hand, intake port 7
The timing valve 18 is opened and closed at certain times relative to the crank angle, and the timing valve 18 is closed at the intake port 7 at low load.
It opens faster and closes faster. As a result, when the load is low, intake air is supplied to the combustion chamber 5 during the overlap period when both the timing valve 18 and the intake port 7 are open. and,
The opening/closing timing of the timing valve 18 is controlled according to the operating state of the engine so that it is delayed as the load increases, and the filling amount is controlled by lengthening the overlapping period when both valves 6 and 18 are open, that is, the intake period. It will increase.

Furthermore, the fuel injection control by the controller 21 leans the air-fuel ratio in a medium-load, medium-speed range, etc., where the required output is low and stability is ensured, and enriches the air-fuel ratio in a high-load, high-speed range, etc. The fuel injection amount is controlled so that the Further, even in the lean region, when the engine temperature is low, lean operation is not performed, and when the engine temperature rises to a predetermined value or higher, lean operation is performed.

In the air-fuel ratio control as described above, when the air-fuel ratio suddenly changes from a rich region to a lean region at low load, for example, the opening/closing timing of the timing valve 18 is delayed so that the filling amount increases in order to compensate for the decrease in output. This increases the amount of overlap. Conversely, during rich transition, the timing of the timing valve 18 is advanced. Timing valve 1 due to this air-fuel ratio fluctuation
The change in step 8 is performed only when the air-fuel ratio fluctuates, and once the transition has occurred, the timing is returned to the original timing.

The control of the timing valve 18 and shutter valve 17 by the controller 21 is controlled by a second
The process will be explained according to the flowchart shown in the figure (only the main parts are shown). After the start, the controller 21 controls the boost P (intake pressure) based on the signal from the boost sensor 26, the engine speed N based on the signal from the crank angle sensor 24, and the intake air amount sensor 12 in step S1.
Read the intake air amount Qa from each. In step S2, the intake port 7 is
The target overlap amount _A1 between the open period of the timing valve 18 and the open period of the timing valve 18, that is, the intake period (filling amount) is calculated.

Then, in step S3, it is determined whether or not the current state is in the lean region, and if YES is in the lean region, the step
In S4, it is determined whether or not it was in the rich area last time.
When the judgment in step S4 is YES and the rich region shifts to the lean region, in step S6 the torque change amount ΔT (decrease) during lean transition corresponding to the air-fuel ratio change ΔA/F is calculated, and in step S7 this torque An overlap correction amount ΔA (increase) of the timing valve 18 is calculated from the change ΔT. Step S9 corrects the target overlap amount _A1 obtained in step S2 using the correction amount ΔA,
Based on this corrected target overlap amount _A1 , the timing of the timing valve 18 is corrected in the direction of delay in step S10.

On the other hand, if the determination in step S3 is NO and the current state is in the rich region, it is determined in step S5 whether or not it was in the lean region last time. This step S5
When the judgment is YES and the transition has occurred from the lean region to the rich region, the process proceeds to step S6, where the torque change ΔT (increase) corresponding to the air-fuel ratio change ΔA/F during the rich transition is calculated in the same manner as during the lean transition. In step S7, the overlap correction amount ΔA of the timing valve 18 is determined from this torque change ΔT.
(decrease) is calculated, and the timing of the timing valve 18 is corrected in the advancing direction.

Furthermore, when the determination in step S5 above is NO,
Or, if the determination in step S4 is NO,
When the air-fuel ratio is in the rich region or lean region and there is no change, the overlap correction amount ΔA is set to 0 in step S8, and the process proceeds to step S9, in which the timing of the timing valve 18 is not corrected.

The setting of the air-fuel ratio control region in the determination in steps S3 to S5 above is such that, for example, in the relationship between the load based on the boost P and the engine rotation speed N, the low load low speed region and the high load high speed region are rich regions. , the medium load and medium rotation region is the lean region, and the area between the rich region and the lean region is set as the stoichiometric air-fuel ratio region. The above-mentioned rich region is intended to ensure stability in the idle region where the amount of fuel is small and to ensure output at high loads and high rotations, while the lean region is intended to improve fuel efficiency in regions where no output is required. It is something.

With the above configuration, when the output fluctuates due to a sudden change in the air-fuel ratio during low load, the timing of the timing valve 18 is changed in a direction to reduce this output fluctuation to correct the filling amount, thereby reducing the torque shock. This is to reduce the occurrence of At this time, the shutter valve 17 is in the closed state and the pumping loss reducing effect by the timing valve 18 is maintained.

In the above embodiment, the intake air volume adjustment during high load is performed by the shutter valve 17 provided for each cylinder, but this intake air volume adjustment is performed by a slot common to all cylinders further upstream. A torque valve may be provided, and a shutter valve that is simply closed during light loads may be interposed in the high-load intake passage.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an engine equipped with an intake system according to an embodiment of the present invention, and FIG. 2 is a flow chart for explaining the operation of a controller. 1...engine body, 4...piston, 6...
Intake valve, 7...Intake port, 10...Intake passage, 10a...Intake passage for high load, 10b...Intake passage for low load, 17...Shutter valve, 1
8...Timing valve, 19...Timing control means, 20...Opening degree control means, 21...Controller.

Claims (1)

[Claims] 1. The intake passage consists of a high-load intake passage and a low-load intake passage, and the high-load intake passage is provided with a shutter valve that closes at low loads, while the low-load intake passage is provided with a timing valve. In an engine in which the closing timing of the timing valve is earlier than the closing timing of the intake port during low load, when the air-fuel ratio is changed under low load, the timing control of the timing valve is used to reduce torque fluctuations accompanying the air-fuel ratio change. An engine intake device characterized by comprising a controller for correcting a filling amount.