JPS62225708A - Valve system for multicylinder engine - Google Patents

Abstract

PURPOSE:To simply uniformize a combustion pressure among cylinders, by a method wherein a leak down time of each of rush adjusters positioned facing their respective cylinders having a low combustion pressure is set to a value lower than that of a cylinder having a high combustion pressure. CONSTITUTION:The upper end parts of valve stems 10a and 11a of suction and exhaust valves 10 and 11, opening and closing suction and exhaust ports 4a and 4b, respectively, in a cylinder head 4 through the working of a hydraulic type rush adjuster 13, are brought into contact with the outer end part of each locker arm 9, and the valves 10 and 11 are opened and closed against a spring 12 along with rocking of each locker arm 9. In this device, each of rush adjusters 13, respectively positioned facing second and third cylinders 2b and 2c, reduced in a pressure due to the shape of suction manifold 2 and the ignition order of cylinders 2a-2d, has a leak down time which is set to a value lower than that of each rust adjuster 13 corresponding to each of first and fourth cylinders 2a and 2b having a relatively high combustion pressure.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a valve train for a multi-cylinder engine equipped with a hydraulic lash adjuster. This relates to measures to equalize combustion characteristics among cylinders.

<Prior Art> Generally, in a multi-cylinder engine, there is some variation in combustion pressure among the multiple cylinders, and this variation causes problems such as increased vibration and noise.

Factors that cause this variation in combustion pressure between cylinders include variations in the combustion state among the cylinders, differences in intake air filling efficiency, and the like. 7i, if the distribution of fuel to each cylinder is poor, and if there is turbulence in the intake air in the combustion chamber within the cylinder or a large temperature difference between the cylinders, variations in the combustion state will occur between the cylinders.

Furthermore, variations in the efficiency of filling intake air into each cylinder occur due to the shape and length of the intake pipe, or the firing order of the cylinders.

For example, for a four-cylinder engine having an ignition order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, a collecting pipe section and a branch pipe section branching from the collecting pipe section and connecting to each cylinder. When two intake manifolds are combined, the inflow direction of the intake air toward the second and third cylinders changes greatly in the collecting pipe section of the intake manifold compared to the first and fourth cylinders. The intake air filling efficiency for the cylinder is reduced. Furthermore, even when a four-cylinder engine with the same ignition order is combined with an intake pipe consisting of a surge tank and an independent pipe section connected from the surge tank to each cylinder, the flow direction and flow of intake air in the surge tank The distance is between the 2nd and 3rd cylinders and the 1st and 4th cylinders.
Since it changes depending on the cylinder, the intake air filling efficiency of the second d3 and third cylinder becomes low.

Therefore, as a technology to correct such changes in intake air filling efficiency between cylinders and the resulting variations in combustion pressure, we have developed
Conventionally, as shown in Japanese Patent Publication No. 51-41171, for example, the length of the intake pipe connected to the engine is long and the pipe resistance is large (L/1:C, in this case, The cam profile of the valve train in the outer cylinders (for example, the 1st and 4th cylinders in a 4-cylinder engine) with low intake air filling efficiency, and the cam profile of the valve train in the outer cylinders with a short intake pipe length and low pipe resistance (for example, the 1st and 4th cylinders in a 4-cylinder engine). By changing the cam profile in the third cylinder) and setting the operation of the intake valve corresponding to the outer cylinder to a low-speed type in which the valve opening timing is late and the valve closing timing is early, variations in intake filling efficiency between each cylinder are reduced. Some proposals have been made to reduce this.

(Problem to be Solved by the Invention) However, in this proposal, the cam profile of the camshaft itself is changed, which increases the number of man-hours for manufacturing the camshaft and increases the cost. There were problems such as a lack of compatibility due to the standardization of engines, and an inability to deal with variations between engines.

(Objective of the Invention) The present invention has been made in view of the above points, and its purpose is to focus on a hydraulic lash adjuster provided in the valve train of a multi-cylinder engine to automatically adjust the valve clearance. By effectively utilizing the characteristics of the adjuster to eliminate variations in combustion pressure between cylinders, it is possible to easily and easily eliminate the need to change the basic structure of parts such as changing the cam profile. The aim is to equalize the combustion pressure between each cylinder.

(Means for Solving the Problem) In order to achieve this object, the solvers of the present invention have developed a valve train for a multi-cylinder engine that is equipped with a hydraulic lash adjuster in at least one of the intake system and the exhaust system. This is a premise. In this valve train, the leak down time of the hydraulic lash adjuster corresponding to a cylinder with low combustion pressure due to a decrease in intake air filling efficiency, for example, is made smaller than the same leak down time of a cylinder with high combustion pressure. In other words, set it to be on the low speed side.

The leak down time of the above-mentioned hydraulic lash adjuster indicates the plunge or sinking characteristics due to the leakage of operating oil from the hydraulic chamber, and is expressed as the time it takes for the plunger to sink by a predetermined amount when a constant load is applied. When the leak down time is short, the plunger sinks in a short time, so the lift characteristics of the valve are corrected to decrease the amount of lift, and the valve opening timing is delayed and the valve opening timing is advanced.

Also, this leak down time characteristic is due to the clearance w between the plunger and the main body of the lash adjuster.
It is changed not only by adjusting the 4-way adjustment, but also by adjusting the load of the valve spring that acts on the lash adjuster.

(Function) Therefore, with the above configuration, in the present invention, since the leak down time of the hydraulic lash adjuster corresponding to the cylinder with low combustion pressure is small, the intake/exhaust valve of that cylinder is・Compared to an exhaust valve, the valve opens relatively later and closes earlier. Therefore, in cylinders with low combustion pressure, as the exhaust valve closes timing advances and the intake valve opens timing retards, the opening overlap period of both valves becomes known, and the dilution gas flows into the intake passage. At the same time, the flow of intake air that has flowed into the cylinder combustion chamber into the exhaust passage is reduced. Moreover, since the opening timing of the intake valve is delayed, the degree to which the piston descends becomes greater before the intake valve opens, increasing the angular pressure in the cylinder, and as soon as the valve opens, intake air is sucked into the cylinder at high speed. In addition to increasing the intake air filling efficiency, the combustion rate also increases due to the increase in the intake air flow rate that flows into the cylinder at once. In addition, advancing the intake valve closing timing suppresses intake air blowback and increases the effective compression ratio, while retarding the exhaust valve opening timing lengthens the holding period of combustion pressure in the cylinder, reducing pressure loss. reduced. These synergistic effects substantially increase the combustion pressure of a cylinder to the same level as that of other cylinders, thereby making it possible to equalize the combustion characteristics among each cylinder of the engine.

Moreover, since this level of combustion pressure can be achieved only by adjusting the leak down time characteristics of the hydraulic lash adjuster, there is no need to change the basic structure of the parts.
In addition to avoiding cost increases, it is also possible to standardize parts and deal with variations between engines.

(Example) Embodiments of the present invention will be described below based on the drawings.

2 and 3, 1 indicates the first cylinder 2a, the third cylinder
An overhead cam type four-cylinder engine having four cylinders 2a to 2d set in the firing order of cylinder 2C, fourth cylinder 2d, and second cylinder 2b, 3 is the cylinder block of engine 1, and 4 is the cylinder head. , a banana-shaped intake manifold 5 forming an intake passage for supplying intake air into each cylinder 2a to 2d on each side of the cylinder head 4;
It is connected to an exhaust manifold 6 that forms an exhaust passage for discharging exhaust gas from each of the cylinders 2a to 2d.

Above the cylinder head 4 is the engine crankshaft 1r.
A camshaft 7 that is rotationally driven by a foot (not shown) is rotatably supported, and the camshaft 7 is formed with a pair of cam surfaces 7a, 7a corresponding to each of the cylinders 2a to 2d. . Reference numerals 8 and 8 indicate a pair of rocker shafts arranged and supported on the cylinder head 4 on both sides of the force ramshaft left 7 in parallel thereto, and 9 indicates each cylinder 2a to 2d of each rocker shaft 8 at a central boss portion 9a. The rocker arms 9 are swingably supported outwardly at portions corresponding to the cam surfaces 7a of the camshaft 7, and the inner ends of each rocker arm 9 are connected to the cam surface 7a of the camshaft 7.
The rotation of the camshaft 7 causes each rocker arm 9 to swing by a predetermined angle.

On the other hand, a cylinder head 4 is connected to the outer end of each rocker arm 9 via a hydraulic lash adjuster 13, which will be described later.
The upper ends of the valve stems 10a and 11a of the intake and exhaust valves 10.11 that open and close the eight intake and exhaust ports 4a and 4b are in contact with each other, and as each rocker arm 9 swings, the valves 10.11 are moved by the valve springs. It is configured to open and close at a predetermined timing by pressing against the urging force of 12.

As shown in enlarged detail in FIG. 1, the load from the camshaft 7 is applied to the outer end of each rocker arm 9, which is in contact with the upper end of the valve stems 10a and Iia of the eight intake and exhaust valves 10.11. A hydraulic lash adjuster 13 is provided which communicates with the valve 10.11. Further, a reserve chamber 14 is formed in the rocker arm 9 corresponding to the lash adjuster 13, and the reserve chamber 14 is communicated with the boss portion 9a of the rocker arm 9 through an oil passage 15 formed in the rocker arm 9. The oil fed to the boss portion 9a is supplied to the lash adjuster 13 (hydraulic chamber 19, which will be described later) via an oil passage 15.

The hydraulic lash adjuster 13 is connected to the rocker arm 9.
The cylindrical adjuster body 17 is fitted into the fitting recess 16 formed on the ICC right side, and the adjuster body 17 is fitted into the fitting recess 16 formed in the
The adjuster body 17 and the plunger 18 define a hydraulic chamber 19, and one hydraulic chamber is provided within the adjuster body. 17 is communicated with the reserve chamber 14 through a communication hole 20 opened at the bottom thereof. Further, a plunger 1r spring 21 is compressed between the adjuster body 17 and the plunger 18 so as to bias the plunger 18 downward (toward the valve 10, 11 side). A check valve 25 is disposed therein, and includes a check valve ball 22 that opens and closes the communication hole 20, and a check valve spring 24 that biases the check valve ball 22 in the valve-closing direction between the check valve ball 22 and the valve retainer 23. There is. Therefore, if a gap occurs between the rocker arm 9 and the cam surface 7a of the camshaft 7 or the valve stems 10a, 11a of the valves 10.11, the plunger 18 will be pushed toward the valves io, 11 by the biasing force of the plunger spring 21. The check valve 25 opens due to the accompanying pressure drop in the hydraulic chamber 19, and the oil in the reserve chamber 14 flows into the communication hole 20.
As a result, the lash adjuster 13 expands as a whole to fill the gap, and the check valve 25 closes due to the increase in pressure in the hydraulic chamber 19, causing oil to flow into the hydraulic chamber 19. The inflow is configured to be stopped. Note that even if a load is applied to the lash adjuster 13 from above and below, the oil that has flowed into this single hydraulic chamber will not flow back into the reserve chamber 14 due to the sealing action of the check valve 25.
It becomes a rigid body while being confined in the cam shirt 9, and thereby the load from the cam shirt 1-7 is reliably transmitted to the valve 4.

Further, as a feature of the present invention, hydraulic lash adjusters 13.13. . . , for each lash adjuster 13 corresponding to the second and third cylinders 2b and 2c, where the combustion pressure is low due to the shape of the intake manifold 5 and the firing order of the cylinders 2a to 2d, the leakage down The first and fourth cylinders 2a, 2d whose combustion pressure is relatively high
The leak down time of each lash adjuster 13 is set smaller than the leak down time of each lash adjuster 13 corresponding to the leak down time. In this embodiment, the leak down time of the lash adjuster 13 is variably adjusted by the clearance between the adjuster body 17 of the adjuster 13 and the plunger 18 fitted therein. 3 cylinder 2b,
The clearance of the lash adjuster 13 corresponding to cylinder 2c is set larger than the clearance of the lash adjuster 13 corresponding to the first and fourth cylinders 2a and 2d.

Therefore, in the above embodiment, due to the shape of the intake manifold 5 and the firing order among the cylinders 2a to 2d, the intake filling efficiency of the second d5 and third cylinders 2b and 2c is lowered, and the combustion pressure thereof is lower than that of the other cylinders. 1st and 4th cylinders 2a, 2d
try to be lower than

However, the second and third cylinders 2b and 2, which have low combustion pressure,
Since the leak down time of the lash adjuster 13.13 of the intake system and exhaust system corresponding to c is set to be smaller than that of the first and fourth cylinders 2a and 2d, which have high combustion pressure, At this time, as shown in FIG. 4, the cam lift characteristics change between the second and third cylinders 2b and 2c and the first and fourth cylinders 2a and 2d, and the second and third cylinders 2b and 2c change. The cam lift characteristic of the engine 2c becomes a low-speed type, and the opening timing of the intake valve 10 shifts to the delayed side, and its lift level also becomes smaller. For this reason,
The A-burlap period with the opening period of the exhaust valve 11 is shortened, the inflow of dilution gas into the intake passage is suppressed, and the blowing of intake air that has flowed into the combustion chamber into the exhaust passage is reduced. Combustion condition improves. Moreover, the negative pressure in the cylinder increases due to the delay in the opening timing of the intake valve 10, and the intake air flows in at a high speed at the same time as the valve 10 opens, increasing the filling efficiency and reducing the valve lift. Therefore, the intake air inflow a degree increases further, and this increase in the intake air flow speed increases the combustion speed.

In addition, as shown in the figure, the opening timing of the exhaust valve 110 is delayed and the closing timing of the intake and exhaust valves 10 and 11 is advanced, which increases the period during which the combustion pressure is maintained and prevents inflowing intake air from entering the intake passage. Blowing back suppression and intake/exhaust valves 10.1
The valve opening overlap period in step 1 can be shortened.

As a result, the combustion state of the second and third cylinders 2b and 2C becomes better, and their combustion pressures are corrected to the rising side and become equal to those of the first and fourth cylinders 2a and 2ti, so that all the cylinders 2a By equalizing the combustion pressure of ~2d, it is possible to significantly reduce the photographing of the engine 1, etc.

Furthermore, since the combustion pressures between the cylinders 2a to 2d are equalized by changing and adjusting the leak down time characteristics of the hydraulic lash adjuster 13 in the valve train, the cam profile between the cylinders 2a to 2d is changed as before. No need to change, preventing cost increase due to increase in manufacturing man-hours9
It is possible to improve compatibility by standardizing parts and deal with variations between engines, and it is possible to make adjustments after the engine is assembled, making it simple and easy to equalize the combustion pressure between cylinders 2a to 2d. can be achieved.

In the above embodiment, the second and third cylinders 2b.

Although the leak down time characteristic of each hydraulic lash adjuster 13 corresponding to 2C is adjusted by the clearance between the adjuster body 17 and the plunger 18, it can also be adjusted by the spring force of the valve spring 12. In other words, in that case, the clearance between the adjuster body 17 of each lash adjuster 13 and the plunger 18 is adjusted to be the same, and the spring force of each valve spring 12 corresponding to the second and third cylinders 2b and 2c is increased. Just let it happen.

Further, in the above embodiment, the engine 1 was targeted in which the combustion pressure between air Ii'2I2a to 2d varies due to variation in intake air filling efficiency due to the shape of the intake manifold 5 and cylinder ignition order. Fluctuations in combustion pressure also occur due to variations in combustion conditions due to fuel distribution, cylinders, turbulence of intake air in combustion chambers, temperature differences between cylinders, and the like.

In that case, it is preferable to set the leak down time characteristic of the hydraulic lash adjuster corresponding to the cylinder where the combustion pressure is low to be smaller than that of other cylinders.

Furthermore, although the above embodiment assumes that the engine 1 is equipped with a hydraulic lash adjuster 13 in both the intake system and the exhaust system, it is also applicable to an engine equipped with a lash adjuster in only one of the intake and exhaust systems. can.

Furthermore, it goes without saying that the present invention can be applied to multi-cylinder engines other than four cylinders.

(Effects of the Invention) As explained above, according to the present invention, a hydraulic lash adjuster is provided in the valve train of a multi-cylinder engine, and the leak down time of the hydraulic lash adjuster corresponding to the cylinder with low combustion pressure is reduced. By making the lash adjuster smaller than that of the cylinder with high combustion pressure, the valve lift characteristics of the intake and exhaust valves in the cylinder with low combustion pressure are set to the low speed side, and the combustion pressure is adjusted to improve intake filling efficiency and combustion speed. By increasing the number of cylinders, it can be made substantially the same as other cylinders, thereby equalizing the combustion pressure between cylinders without increasing costs or reducing component compatibility, thereby reducing vibration and noise in multi-cylinder engines. It is something that can be done.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an enlarged sectional view of a hydraulic lash adjuster, and FIG. 2 is a cross-sectional view of the hydraulic lash adjuster.
3 is a plan view showing the valve operating system of a multi-cylinder engine, and FIG. 4 is a characteristic diagram showing the lift characteristics of the intake and exhaust valves. DESCRIPTION OF SYMBOLS 1... Engine, 2a-2d... Cylinder, 7... Camshaft, 9... Rocker arm, 10... Intake valve, 11... Exhaust valve, 12... Valve spring, 13...・Hydraulic lash adjuster, 17...
・Adjuster body, 18... Plunger, 19...
Hydraulic room. Patent applicant Mazda Motor Corporation representative
Rinto Mae 1) Hiroshi 1
．． .

Claims (1)

[Claims] (1) In a valve train for a multi-cylinder engine equipped with a hydraulic lash adjuster in at least one of the intake system and the exhaust system, the leak down time of the lash adjuster corresponding to the cylinder with low combustion pressure is longer than that of the cylinder with high combustion pressure. A valve train for a multi-cylinder engine characterized by being set to be small.