JPH07116981B2 - Engine intake system - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intake device for an engine.

(Prior Art) At the time of light load operation of the engine, a relatively large intake negative pressure is generated downstream of the throttle valve in the throttled state, and this intake negative pressure causes the piston in the intake stroke to perform negative work,
It is generally known that a so-called pumping loss occurs.

On the other hand, the intake passage downstream of the throttle valve is branched into a main intake passage and a sub intake passage, a closing valve is provided in the main intake passage for closing at low load operation, and a rotary on-off valve is provided in the sub intake passage. There is a technique of reducing the pumping loss by closing the rotary valve early in the middle of the stroke (for example, Japanese Patent Laid-Open No. 58-23245).
(See the official gazette). In other words, this technology reduces the throttle valve throttle degree and introduces intake air in a state close to atmospheric pressure, and cuts off intake air early to reduce the amount of intake air introduced to suit low-load operation. , The negative work of the piston is reduced to reduce the pumping loss.

In addition, the method is not limited to the method of cutting off the intake air early as in the above technology, and the intake port is opened until after the bottom dead center,
It is also generally known that by returning a part of the intake air that has been once introduced, it is possible to introduce the intake air in a state close to the atmospheric pressure while suppressing the intake air introduction amount to an appropriate amount to reduce pumping loss. There is also a technique for reducing the pumping loss by changing the valve closing timing of the intake valve itself without using the rotary valve (for example, Japanese Patent Publication Sho 58
-10573).

(Problems to be Solved by the Invention) By the way, at the time of deceleration of the engine, there is a demand to enhance the feeling of deceleration by utilizing the pumping loss to apply the engine brake, and at the time of deceleration, the engine speed is Generally, there is a demand for stopping fuel supply to the engine to improve fuel efficiency when the throttle valve is high and the throttle valve is close to fully closed.

However, in the state where the pumping loss reducing means as described in the above-mentioned prior art is operated, on the contrary, there is a problem that the performance of the engine brake is lowered and a sufficient feeling of deceleration cannot be obtained. On the other hand, it is possible to stop the operation of the pumping loss reduction means at the time of deceleration, but when returning from the state where the fuel supply is stopped to restart the fuel supply, it is possible to cooperate with the operation restart of the pumping loss reduction means. As a result, the torque in the deceleration direction suddenly becomes small, which causes a relatively large torque shock. That is, stopping the operation of the pumping loss reducing means to obtain a feeling of deceleration and reducing the torque shock at the time of fuel recovery have the contradictory properties that if one is solved, the other is not solved. There is a problem that it is a requirement and it is difficult to solve at the same time.

(Means for Solving the Problems) As a means for solving the contradictory problem, the present invention stops the operation of the pumping loss low range means at least in the operation range where the fuel supply is stopped at the time of deceleration, while the fuel supply is stopped. (EN) Provided is an intake system for an engine, which is provided with a control means for activating a pumping loss reducing means prior to the return when restarting.

(Operation) In the intake system of the engine, the pumping loss low range means is deactivated in at least the operation range where the fuel supply is stopped during deceleration, so that the engine braking effectively utilizing the pumping loss can be applied. It is possible to enhance the feeling of deceleration. Since the pumping loss reduction means operates prior to the fuel recovery, the deceleration torque is reduced by one step, and then the fuel supply is restarted and the deceleration torque is further reduced. Therefore, there is no sudden change in the deceleration torque due to the return of the fuel.

(Effect of the Invention) Therefore, according to the present invention, it is possible to obtain the effect of suppressing the torque shock at the time of fuel recovery while ensuring the engine braking performance at the time of engine deceleration.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In this embodiment, a quick closing system of the intake valve is adopted as a pumping loss reducing means, and the whole structure is shown in FIG. In the figure, 1 is an engine body in which a piston 3 is fitted in a cylinder 2. In the intake system, an air cleaner 4, an air flow meter 5, and a throttle valve 6 are provided in this order from the upstream side, and a first passage 7 branched downstream of the throttle valve 6 and a second passage 9 with a shutter valve 8 interposed between the intake side and the intake side. Meet at port 10.

The intake port 11 has an intake valve 11 and the exhaust port
Exhaust valves 13 are provided on the respective valves 12, and a fuel injection valve 14 faces the intake port 10 from the downstream side of the shutter valve 8. Then, with respect to the timing switching means (pumping loss reducing means) 15 of the intake valve 11, the actuator 16 of the shutter valve 8 and the fuel injection valve 14,
A control signal is output from the controller (control means) 17. Further, the controller 17 has parameters for controlling the intake air amount (load) signal from the air flow meter 5, the opening signal of the throttle valve 6, the engine speed signal from the crank angle sensor 18, and the water temperature sensor of the engine body 1. The water temperature signal from 19 is provided.

The concrete structure of the timing switching means 15 of the intake valve 11 is shown in FIGS.

That is, in FIG. 2, 21 is a normal rocker arm for closing the intake port 10 after the bottom dead center of the piston 3 in the intake stroke, and 22 is a rocker arm for closing the intake port 10 before the bottom dead center. , Are respectively supported by the rocker shaft 23. Further, 24 is an exhaust rocker arm supported by an exhaust rocker shaft 24a.

The early closing rocker arm 22 comes into contact with the stem of the intake valve 11 via the valve adjusting screw 25, and the normal rocker arm 21 can be engaged / disengaged by the select plate 28 with respect to the center shaft 27 in the engagement hole 26 provided in the upper portion thereof. The intake valve 11 is lifted via the center shaft 27 and the early closing rocker arm 22. In FIG. 2, 29 is a retainer of the valve spring 30, 31 is a camshaft, and 32 is an oil pipe described later.

The engine of this embodiment is provided with two intake valves per cylinder. As shown in FIG. 3, the early closing rocker arm 22 has valve adjusting screws 25, 25 for the two intake valves.
Have. Further, the normal rocker arm 21 is in contact with the normal cams 34, 34 on both sides of the early closing cam 33 with which the early closing rocker arm 22 is in contact. The select plate 28 is capable of advancing and retracting in the groove 35 formed in the normal rocker arm 21 in the axial direction of the rocker shaft 23 by a hydraulic cylinder 36, and its specific structure is shown in FIG.

That is, the select plate 28 is engaged with the large hole portion 37 that allows the relative movement of the center shaft 27 in the axial direction, and the notch groove 27a of the center shaft 27 that is continuous with the large hole portion 37 to prevent the movement. It has a small hole portion 38 and is connected to the switching piston 39 of the hydraulic cylinder 36. In this case, the switching piston 39
Receives oil pressure from the oil pipe 32 to the back via the oil passage 41 and the oil chamber 42, advances the select plate 28 in the direction of engagement with the center shaft 27, and retracts it by the return spring 43.

Next, the controller 17 will be described. As shown in FIG. 5, the controller 17 performs an operation range determination means 45 for determining an engine operation range, a deceleration determination means 46 for determining a deceleration operation of the engine, and an acceleration operation of the engine. Acceleration determination means 47 for determination, opening / closing signal output portion 48 for shutter valve actuator 16, switching signal output portion 49 for valve timing switching means 15, fuel cut signal output portion 50 for fuel injection valve 14, fuel restoration determination means 51, first The delay means 52 and the second delay means 53 are provided.

The operating range determining means 45 determines the engine operating range from the map shown in FIG. 6 based on the engine speed signal and the intake air amount (load) signal, and opens / closes the signal output unit 48, the switching signal output unit 49, and the fuel cut signal output unit. A command is given to 50, the fuel restoration judging means 51 and the acceleration judging means 47. That is, the opening / closing signal output unit 48 receives the shutter valve opening command in the high load region and the shutter valve closing command in the low load region, and gives an operation signal corresponding to the command to the shutter valve actuator 16. Switching signal output section
49 receives a normal command in a high load range and an early closing command in a low load range, and gives an operation signal corresponding thereto to the valve timing switching means 15. The fuel cut signal output unit 50 receives a cut command to stop the fuel supply in an operating range (fuel cut range) in which the throttle valve 6 is closed and the engine speed is relatively high during deceleration, and is not in the fuel cut range. In this case, a fuel return (fuel supply) command is received via the fuel return determination means 51, and an operation signal is given to the fuel injection valve 14.

In the case of the present embodiment, in the valve timing switching means 15, the switching piston 39 is advanced by the normal signal and the small hole portion 38 of the select plate 28 is engaged with the center shaft 27, whereby the normal rocker arm 21 is moved to the select plate 28. Is connected to the center shaft 27 via. Therefore, the intake valve 11 is driven by the normal rocker arm 21 to reach the normal timing for closing the intake port 10 after the bottom dead center has elapsed, as shown in FIG. On the other hand, in the case of an early closing signal, the switching piston 39
Hydraulic pressure is released and retracts, and the select plate 28
The engagement of 27 is released and the connection state of the normal rocker arm 21 to the center shaft 27 is released. Therefore, the intake valve 11 is driven only by the early-closing rocker arm 22, and the early-closing timing comes before the intake port 10 is closed before the bottom dead center.

On the other hand, the deceleration determination means 46 determines deceleration from the closing movement of the throttle valve 6 and gives a deceleration signal to the switching signal output section 49 and the fuel cut signal output section 50. In this case, the switching signal output section 49
When receiving the deceleration signal, gives a normal signal to the valve timing switching means 15 in preference to the command from the operating range determining means 45. Further, the fuel cut signal output unit 50 gives a cut signal to the fuel injection valve 14 when it receives a deceleration signal and a cut command from the operating range determination means 45.

The fuel recovery determining means 51 detects the transition from the fuel cut area to the fuel supply area to determine the fuel recovery, and the switching signal output section 49
To the fuel cut signal output unit 50 via the first delay means 52. In this case, the first delay means 52 delays the output of the return instruction so that the fuel supply from the fuel injection valve 14 is restarted after the valve timing switching means 15 is actually switched to the early closing timing by the early closing instruction. .

Further, the acceleration determination means 47 detects the transition from the shutter valve closed region to the shutter valve opened region, determines acceleration, gives a normal command to the switching signal output section 49, and also outputs an opening / closing signal via the second delay means 53. A shutter valve open command is given to the output unit 48. In this case, the second delay means 53 delays the output of the shutter valve open command so that the shutter valve 8 is opened after the valve timing switching means 15 is actually switched to the normal timing by the normal command.

The flow of control from deceleration to fuel recovery after fuel cut is shown in Fig. 8. After initialization, data (intake amount signal, rotation speed signal, throttle opening signal)
Is read and it is determined whether or not the vehicle is decelerating (steps S _{1 to} S ₃ ). Valve timing when the deceleration is determined is switched to normal, when it is determined that a further fuel cut region, the flag is the fuel cut signal is output erected (Step S ₄ ~S _7).

When the supply of fuel is resumed is determined not to be a fuel cut zone at the step S _5, the present time is to verify whether the fuel cut state by the presence or absence of the flag, the valve timing after the flag processing time of the fuel cut state is normal Is switched to early closing, and a timer (first delay means 5
2) it is activated (step S ₈ to S _10). Then, after the set time has elapsed, the fuel return signal is output (step S ₁₁ ,
S ₁₂ ).

Therefore, at the time of deceleration, the valve timing is the normal timing even if it is the early closing timing in the operating range determination, and therefore the pumping loss is used to increase the torque in the deceleration direction to obtain a deceleration feeling. be able to. In the return after the fuel cut, the valve timing is first switched from normal to early closing to lower the deceleration torque by one step, and then the deceleration torque is lowered by the return of the fuel. That is, the deceleration torque is gradually reduced to prevent a sudden change in the torque, and the torque shock is alleviated.

Although the valve timing after the fuel is returned is in the early closing state, it may be set to be normal in order to secure combustion stability in the extremely low load range even when the engine load is not high.

The flow of control during acceleration is shown in Fig. 10. After initialization and data reading, if the shutter valve is closed, a flag is set, and if the shutter valve is open, the presence or absence of the flag is confirmed. (step S ₁ ~S _5). That is, if the flag is set, it is determined that the operating state of the engine is during acceleration when the shutter valve closed region is shifted to the shutter valve opened region (the shutter valve opened state is not continued). If it is during acceleration, a valve timing switching signal from early closing to normal is output after flag processing, and a timer (second delay means 53)
There actuated, the shutter valve opening signal is output after a lapse of the set time (Step S ₆ ~S _9).

Therefore, the output torque of the engine first becomes higher by switching the valve timing, and then becomes higher by opening the shutter valve 8. That is, since the torque gradually increases, the torque shock is alleviated. To alleviate the torque shock at the time of acceleration, the shutter valve 8 is opened sequentially from the cylinder whose valve timing has been switched, or the fuel correction during acceleration is changed between the cylinder whose valve timing has been switched and the cylinder which does not. May be adopted.

As the pumping loss reducing means, besides the method of switching the valve timing by switching the rocker arm, a cam whose profile changes due to axial displacement or a plurality of cams with different profiles are used, and the valve timing on this cam side May be adopted, a method of changing the opening / closing timing of the intake port using a rotary valve, or the like, and a method of reducing the pumping loss by the late closing method of the intake port may be adopted.

[Brief description of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is an overall configuration diagram of an intake device of an engine, Fig. 2 is a vertical cross-sectional view of a valve mechanism, Fig. 3 is a plan view of the same, and Fig. 4 is the same mechanism. Fig. 5 is a block diagram of the control type, Fig. 6 is an engine operating range characteristic diagram, Fig. 7 is a valve timing characteristic diagram, Fig. 8 is a control flow chart during deceleration, FIG. 9 is a time chart of the deceleration torque, and FIG. 10 is a flow chart of control during acceleration. 1 ... Engine body, 10 ... Intake port, 11 ... Intake valve, 14 ... Fuel injection valve, 15 ... Valve timing switching means (pumping loss reducing means), 17 ... Controller (control means).

Claims (1)

[Claims] 1. An engine equipped with pumping loss reducing means for reducing pumping loss due to reciprocating movement of a piston, wherein the operation of the pumping loss reducing means is stopped at least in an operating range where fuel supply is stopped during deceleration. An intake system for an engine, comprising: a control means for operating a pumping loss reduction means prior to the return when the fuel supply is resumed.