JPH0580561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake valve control device for a diesel engine, and more particularly to one that obtains the opening period timing of the intake valve in accordance with the load of the engine.

(Prior art) Generally, the opening timing of an engine's intake valve (the timing at which intake ends) is set at 30 to 60 degrees after bottom dead center, but it can be variably controlled depending on the operating state of the engine. is preferred. For example, JP-A-55-69715
The publication describes that in a reciprocating engine, the lift amount of the intake valve is variably controlled using a three-dimensional cam so that the valve closing timing of the intake valve is earlier in the intake stroke when the load is low, or becomes later in the compression stroke when the load is low. Accordingly, a system has been shown in which the amount of intake air is controlled in accordance with the load of the engine to reduce pumping loss.

(Problem to be solved by the invention) On the other hand, in a diesel engine, since no load is applied when the engine starts and the rotational speed is low, it is preferable to close the intake valve almost at bottom dead center because this increases the amount of effective work. . Further, at low load, the piston speed and inertia increase compared to when starting, so it is preferable to close the piston as soon as possible after bottom dead center in order to reduce compression work and improve fuel efficiency. Furthermore, when the load is high, it is preferable to close the valve as late as possible after bottom dead center in order to increase the intake air filling amount and reduce smoke. In other words, it is preferable that the closing timing of the intake valve be made later in the range of 0° to a maximum of 60° after the bottom dead center in higher load regions, or in other words, earlier in lower load regions.

By the way, in diesel engines, high compression,
Due to the small volume, the top surface of the piston is close to the bottom surface of the cylinder head at top dead center, so the intake valve will interfere with the top surface of the piston at maximum lift. You can't make it big. Therefore, it has been difficult to change the valve overlap amount by controlling the lift amount of the intake valve as described above, that is, to change the closing timing of the intake valve in accordance with the engine load.

The present invention has been made in view of the above, and an object of the present invention is to provide a plurality of intake passages opening on the lower surface of the cylinder head and a plurality of intake valves for opening and closing the intake passages, and to provide a valve-opening period for each intake valve. By changing the opening period of at least one intake valve to have separate valve opening periods while keeping the value constant, the end timing of intake intake in a diesel engine can be adjusted depending on the engine load without relying on lift amount control. The object of the present invention is to perform variable control accordingly, thereby making it possible to increase the effective workload at startup, reduce the compression workload at low loads, and increase the intake air filling amount at high loads.

(Means for Solving the Problem) In order to achieve the above object, the solution of the present invention is based on a diesel engine in which the top surface of the piston at top dead center is close to the bottom surface of the cylinder head. Then, the plurality of intake passages that open on the lower surface of the cylinder head and some of the intake passages among the plurality of intake passages are opened and closed, and the end time of intake almost coincides with the bottom dead center, and the valve opening period timing is adjusted. A fixed intake valve, and a variable intake valve that opens and closes the remaining intake passages among the plurality of intake passages, has an opening period that overlaps with the fixed intake valve, and has a variable opening period timing. a variable drive means for shifting the opening period of the variable intake valve; a load detection means for detecting the load state of the engine; and a variable drive means for detecting the load state of the engine; The variable drive means is operated and controlled so that the period timing is changed according to the engine load state, and as the engine load increases, the overlap period is decreased and the intake end timing is delayed from the bottom dead center. It shall be provided with control means to

(Function) This allows the opening periods of the fixed intake valve and the variable intake valve to overlap with each other, while keeping the variable intake valve constant so as not to interfere with the top surface of the piston without making it variable through lift amount control. Transition control of the valve opening period timing of the variable intake valve is performed so as to reduce the overlap period of the valve opening period with the fixed intake valve according to an increase in engine load, and to make the end timing of intake intake later than the bottom dead center. By doing this, the effective work amount is increased by setting the intake end timing to near the bottom dead center when starting the engine.
In addition, when the load is low, the compression work is reduced as soon as possible after the bottom dead center, and when the load is high, the compression work is delayed as much as possible after the bottom dead center to increase the filling efficiency of intake air.

(Effects of the Invention) Therefore, according to the intake valve control device for a diesel engine of the present invention, the opening period of a plurality of intake valves is made constant without controlling the lift amount, and the opening period of some of the intake valves is kept constant. The valve period timing is controlled according to the engine load, and the intake end timing is delayed from the bottom dead center as the load increases. This eliminates interference with the top surface of the piston of the intake valve and improves the cam face. While maintaining the reliability of the valve train by suppressing increases in wear and cam drive resistance, it increases the effective work at engine startup, and improves fuel efficiency by reducing compression work at low loads. This makes it possible to simultaneously reduce smoke by improving intake air filling efficiency during high loads.

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

In Fig. 1 and Fig. 2, 1 is cylinder 2.
3 is a cylinder head joined to the cylinder block 1; 4 is a cylinder head joined to the cylinder block 1;
is a piston that is slidably fitted in the cylinder 2, and a combustion chamber 5 is formed by the cylinder 2, the lower surface of the cylinder head 3, and the upper surface of the piston 4, and the piston 4 is fitted at the top dead center. A diesel engine DE is configured such that its upper surface is close to the lower surface of the cylinder head 3.

6 and 7 are first and second intake passages, respectively, whose downstream ends open at the bottom surface of the cylinder head 3 and communicate with the combustion chamber 5; and 8, an exhaust gas whose upstream ends open at the bottom surface of the cylinder head 3 and communicate with the combustion chamber 5. It is a passage. The opening of the first intake passage 6 to the lower surface of the cylinder head 3 has a valve opening period during which the first intake passage 6 is opened and closed and the end timing of intake (valve closing timing) almost coincides with the bottom dead center. A fixed intake valve 9 with a fixed intake valve 9 is disposed at the opening of the second intake passage 7 to the lower surface of the cylinder head 3, and the second intake passage 7 is opened and closed, and the fixed intake valve 9 is opened and closed. A variable intake valve 10 having valve opening timings with overlapping periods and a variable opening period timing is provided.
Further, an exhaust valve (not shown) for opening and closing the exhaust passage 8 is provided at the opening of the exhaust passage 8 to the lower surface of the cylinder head 3. Further, on the upper part of the cylinder head 3, there are two camshafts 11 and 12 on a fixed side and a variable side that extend parallel to each other.
is installed. The fixed side camshaft 11 has tappets 13 (only the fixed intake valve 9 side is shown) at the upper ends of the fixed intake valve 9 and exhaust valve, respectively, at positions corresponding to the fixed intake valve 9 and exhaust valve.
There are provided cams 14, 15 for fixed intake valves and exhaust valves that abut each other through the cams. On the other hand, the variable-side camshaft 12 has a cam 17 for the variable intake valve that contacts the upper end of the variable intake valve 10 via a tappet 16 at a position corresponding to the variable intake valve 10.
is provided. In addition, both camshafts 1
1 and 12 have a pair of gears 18 at their shaft ends,
The fixed side camshaft 11 is rotatably connected in mutually opposite directions via the fixed side camshaft 11
The shaft end of is drivingly connected to the crankshaft (not shown) of the engine DE via a timing belt 21 wrapped around a pulley 20 provided at the shaft end, and is driven in opposite directions in synchronization with the engine DE. The camshafts 11 and 12 rotate to open and close the intake valves 9 and 10 and the exhaust valves via the cams 14, 15 and 17. The valve period is kept constant so as not to interfere with the upper surface of the piston 4, and as shown in FIG. The valve opening periods are set to have valve opening timings that overlap.

A portion of the variable side camshaft 12 near the shaft end is divided, and helical splines 22 and 23 extending in opposite directions are formed on the outer periphery of each divided portion. Both helical splines 22,
A cylindrical adjustment piece 24 that engages with 23 is fitted to connect the two divided parts. moreover,
A rack 25 is connected to the adjustment piece 24, and a pinion 27 provided on the rotating shaft of a reversible motor 26 is engaged with the rack 25. An operating switch 29 is connected to the operating circuit 28 of the motor 26. When the operating switch 29 is turned ON, the motor 26 is operated to move the adjusting piece 24 in the axial direction through the engagement between the pinion 27 and the rack 25, thereby causing the adjusting piece 24 and the helical spline to move. The variable intake valve 1 of the cam face of the variable intake valve cam 17 through engagement with 22 and 23
The contact timing with respect to 0 changes and the variable intake valve 10
A variable drive means 30 is configured to shift the valve opening period timing.

Further, the operating switch 29 of the variable drive means 30 is ON-OFF controlled by a control means 31, and the control means 31 has an engine DE.
A rotation speed sensor 33 that detects the engine rotation speed is provided on the fuel injection pump 32 driven by the
, a potentiometer 34 which is also provided on the fuel injection pump 32 and serves as a load detection means for detecting the engine load, and the movement position of the rack 25 of the variable drive means 30, that is, the valve opening period timing of the variable intake valve 10. A position sensor 35 for detecting the degree of movement is connected as an input. Thus, the control means 31 includes a rotation speed sensor 33, a potentiometer 34, and a position sensor 3.
Turn the operating switch 29 ON-OFF by each output of 5.
The operation control of the variable drive means 30, that is, the transition degree of the opening period of the variable intake valve 10 is feedback controlled, and the opening timing of the variable intake valve 10 is adjusted as shown in FIG. As shown, the opening period of the variable intake valve 10 and the fixed intake valve 9 overlaps as the load increases in the range from 0° to a maximum of 60° after the bottom dead center. The period is decreased and the end timing of intake is controlled to be later than the bottom dead center, and the rotation speed is controlled by the rotation speed sensor 33.
When the engine speed is 500 rpm or less, it is determined that the engine is starting, and the closing timing of the variable intake valve 10 is set to approximately 0° at the bottom dead center.The opening periods of both intake valves 9 and 10 almost overlap, and the end of intake is approximately reached. It is controlled so that the bottom dead center is 0°.

Therefore, in the above embodiment, when the engine is started, the opening periods of the variable intake valve 10 and the fixed intake valve 9 almost overlap, and the end timing of intake air intake is approximately 0° at the bottom dead center. Almost no load and low rotation speed (500 rpm or less)
Therefore, the amount of effective work at startup can be increased. Furthermore, when the engine is under low load, the overlapping period between the opening periods of the variable intake valve 10 and the fixed intake valve 9 is large, and the end of intake air intake is as soon as possible after bottom dead center, so the compression work can be reduced. , fuel efficiency can be improved. Furthermore, when the engine is under high load, the overlapping period of the open periods of both intake valves 9 and 10 is reduced, and the end of intake air intake is delayed as much as possible after bottom dead center, increasing the intake air filling efficiency and reducing smoke. can do.

In that case, the above-mentioned change in the end timing of the intake air intake is to change the opening period timing of only the variable intake valve 10 among the two intake valves 9 and 10, which have a constant opening period that does not interfere with the upper surface of the piston 4. Since it is carried out by shifting, it is possible to prevent interference with the top surface of the piston as would be the case with lift amount control, and it is also possible to suppress wear on the cam face and increase in cam drive resistance as would be the case when using a three-dimensional cam, thereby improving the valve train. The reliability of the system can be maintained well.

In the above embodiment, the end timing of intake was variably controlled according to the engine load, but in a diesel engine equipped with a catalyst-equipped collection member for collecting particulate components such as carbon particles in the exhaust passage, the exhaust gas When performing regeneration by guiding the regeneration gas to the collection member, if the intake valve control device of the above embodiment is used to advance the end timing of intake suction,
Since it is possible to prevent cooling by reducing the amount of air while ensuring sufficient O ₂ for carbon combustion, it is possible to raise the temperature of exhaust gas from a low temperature of 150°C to around 350°C. The exhaust gas temperature (350° C.) is heated to a higher temperature by the oxidation reaction, and the particulate components such as carbon particles collected by the collection member can be sufficiently burned off.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic vertical sectional view, FIG. 2 is a schematic plan view, and FIG. 3 is an explanatory diagram of valve timing. 3... Cylinder head, 4... Piston, DE... Diesel engine, 6... First intake passage, 7... Second
Intake passage, 9...fixed intake valve, 10...variable intake valve,
30... Variable drive means, 31... Control means, 34... Potentiometer (load detection means).

Claims (1)

[Scope of Claims] 1. In a diesel engine in which the top surface of the piston at top dead center is close to the bottom surface of the cylinder head, a plurality of intake passages open to the bottom surface of the cylinder head, and a portion of the intake passages among the plurality of intake passages. A fixed intake valve that opens and closes a passage, the end timing of intake almost coincides with bottom dead center, and a fixed valve opening period, and a fixed intake valve that opens and closes the remaining intake passages among the plurality of intake passages. A variable intake valve having valve opening timings with overlapping valve opening periods and a variable opening period timing, a variable drive means for shifting the valve opening period timing of the variable intake valve, and a detecting engine load condition. and a load detection means for receiving an output from the load detection means to change the opening period timing of the variable intake valve according to the engine load condition, and reducing the overlap period as the engine load increases. An intake valve control device for a diesel engine, comprising: a control means for controlling the operation of the variable drive means so that the end timing of intake air intake is delayed from bottom dead center.