JP3201147B2 - Valve train for 4-cycle 4-cylinder engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for a four-stroke four-cylinder engine, and more particularly to a valve train for a four-stroke four-cylinder engine in which a camshaft and a power transmission shaft of the engine are connected by a gear train. is there.

[0002]

2. Description of the Related Art In general, a camshaft for opening and closing an intake / exhaust valve has been driven by a chain or a belt. As shown in FIG. 4, a crank gear 1a is attached to a crankshaft 1, a cam gear 2a is attached to a camshaft 2, and the crank gear 1a and the cam gear 2a are provided for the purpose of improving maintenance and maintenance-free performance. Idle gear 3 between
…, A gear train 4 composed of 3a
Gear train driven valve trains have been considered.

[0003] However, in this type of valve train, the rattle noise (gear noise) between the cam gear 2a (driven gear) and the idle gear 3a (drive gear) is large, and high noise is generated from the engine. There was a problem that it would.

Accordingly, the present inventors have proposed that the engine to be tested has 4
Using a four-cycle cylinder diesel engine, tests were conducted on the fluctuation of the rotational torque of the camshaft itself, the fluctuation of the rotational speed, and the height of the gear noise of the gear train. As shown in FIG. Was found to reach a peak when switching from the deceleration state to the acceleration state.

When the camshaft 2 receives a drag from a valve spring when opening and closing the intake / exhaust valve, the camshaft 2 periodically varies in torque (hereinafter referred to as "driving torque variation"). (FIG. 5 (a)), and when the drive torque fluctuation is switched from the deceleration state to the acceleration state, a braking contact phenomenon occurs at the meshing portion between the driven gear 2a and the drive gear 3a, resulting in a large rattle noise (gear noise). ) (FIG. 5 (c)).

In a four-cycle engine, when the crankshaft 1 makes two rotations, the camshaft 2 makes one rotation to complete one stroke (intake → compression → explosion → exhaust).
In a four-cylinder engine, the torque changes four times during one revolution of the camshaft 2, and its cycle T is 180 degrees in crank angle.
°, and the cam angle is 90 °.

Therefore, in order to cancel the fluctuation of the driving torque of the camshaft 2 due to the opening and closing of the intake / exhaust valve, the fluctuation of the torque in the opposite phase to that (hereinafter referred to as “cancel torque fluctuation”)
That. ) May be generated on the camshaft 2, and a rotating body is provided integrally with the camshaft 2, and a dummy cam portion having an angular acceleration characteristic shifted by a cam angle of 45 ° with respect to the period T is provided on the outer peripheral surface thereof. The dummy cam portion may be pressed with a force corresponding to the magnitude of the drive torque fluctuation. Here, while the camshaft 2 makes one rotation, the peak of the drive torque fluctuation is four times, and in order to cancel this with two roller tappets, the interval between the roller tappets is 18
At every 0 °, the number of dummy cam portions becomes a total of 4 at every 90 °.

Based on these results and considerations, the present applicant and others, as shown in FIG. 6, attach a rotating body 6 having nose-shaped dummy cam portions 5 formed at 90 ° intervals on the outer peripheral surface to the camshaft 2. The dummy cam portion 5 is attached coaxially to the end portion and is circumferentially spaced 180 ° outward from the rotating body 6 in the radial direction.
And two roller tappets 7 are disposed so as to be able to contact the outer peripheral surface of the rotating body 6. A valve train (Japanese Patent Laid-Open No. 6-42314) has been devised which is configured to cause the torque fluctuation of the camshaft 2 and has been proposed earlier.

[0009]

SUMMARY OF THE INVENTION According to the above proposal, the gear noise can be reduced.

However, even if the torque fluctuation in the opposite direction to the driving torque fluctuation of the camshaft during intake and exhaust is generated by two roller tappets and four dummy cam parts, the angle from the dummy cam part to the next dummy cam part can be obtained. Therefore, the cam profile of the dummy cam section is limited by the above restriction, and in order to create a cancel torque fluctuation in which the amplitude changes in substantially the same cycle as the drive torque fluctuation, the diameter of the dummy cam must be increased. There was no problem.

It is an object of the present invention to provide a lightweight and small valve train for a four-cycle four-cylinder engine capable of suppressing the breaking contact phenomenon.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a four-cycle four-cycle system in which a crankshaft and a camshaft for driving intake and exhaust valves are connected by a gear train.
In the valve train of a cylinder engine, a substantially elliptical dummy cam is coaxially attached to the end of the camshaft, and is movable in the radial direction at 90 ° intervals in the circumferential direction on the outer peripheral surface of the dummy cam, and A roller tappet is arranged so that it can be brought into contact with the outer peripheral surface of the dummy cam by the resilience. The profile is set so that it can be generated, and the relative position in the circumferential direction between the pair of roller tappets and the dummy cam separated by 180 ° is set so that the cancel torque in the opposite phase to the drive torque fluctuation is applied to the camshaft. is there.

[0013]

According to the above-mentioned structure, it is possible to cancel the fluctuation of the driving torque acting on the cam shaft without increasing the outer diameter of the dummy cam and the outer shape of the casing, to eliminate the braking contact phenomenon, and to eliminate the gear noise. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a valve train for a four-cycle four-cylinder engine according to the present invention will be described below with reference to the accompanying drawings. The description of the same configuration as the conventional one is omitted here.

FIG. 1 is a cross-sectional view of the camshaft viewed from a direction along the axial direction, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

In FIG. 1 or FIG. 2, reference numeral 2 denotes an intake cam 8 and an exhaust cam 9 for opening and closing an intake / exhaust valve (not shown).
And a camshaft 2 having:
A cam gear 2a (driven gear) is integrally attached to one end thereof, and a dummy cam 10 is integrally attached to the other end thereof to cancel a driving torque applied to the camshaft 2. A cylindrical casing 12 is attached to the side of the cylinder head 11 so as to concentrically accommodate the other end of the dummy cam 10 and the camshaft 2.

The cylindrical casing 12 is provided with a housing 13 in a cylindrical shape with a bottom at a portion surrounding the outer peripheral surface (cam face) of the dummy cam 10 at 90 ° intervals in the circumferential direction.
Are formed. The housings 13 are integrally formed with the cylindrical casing 12 such that the axis of the housing 13 intersects the axis of the camshaft 2 and the openings of the housings 13 face the outer peripheral surface of the dummy cam 10, respectively. Is provided.

Each of the housings 13 has a bottom
An elastic body (coil spring or rubber elastic body) 14 accommodates the roller tappet 7 on the dummy cam side.

The roller tappet 7 has a roller 15 at its tip.
And is always pushed out toward the dummy cam by receiving the elastic force of the elastic body 14.
5 can rotate while always in contact with the outer peripheral surface of the dummy cam 10.

Of course, the roller tappet 7 is
The rotation around the axis is regulated by the
Are rotatably supported along the outer peripheral surface of the camshaft 2.

The dummy cam 10 has a short Y-axis direction
It is made of an elliptical member that is long in the direction of the axis 18, and the upper part and the lower part sandwiching the X axis 17 (long axis) form dummy cam parts 20 and 21 independently of each other.

Therefore, the Y of the dummy cam portions 20 and 21
By adjusting the length in the direction of the shaft 18, the length in the direction of the X-axis 17 and the cam profile, and disposing the roller tappets 7 at 90 ° intervals in the circumferential direction outside the outer peripheral surface of the dummy cam 10, the dummy cam 10 Without increasing the outer shape of the casing 12 and the outer shape of the casing 12, the cancel torque can be applied to the camshaft 2 four times per rotation. A cancel torque can be applied to the camshaft 2.

Of course, in order to cancel the driving torque fluctuation by giving the canceling torque to the camshaft 2, the cam profiles of the dummy cam portions 20, 21 have the same cancellation and fluctuation in the cycle and amplitude as the driving torque fluctuation of the camshaft 2. The profile is set to a profile that can cause a torque variation on the camshaft 2. The relative position of the dummy cam 10 and the roller tappet 7 in the circumferential direction is such that the camshaft 2 is provided with a canceling torque variation in the opposite phase to the driving torque variation of the camshaft 2. Is determined to be able to occur.

For example, when the mounting position of the casing 12 is adjusted after the dummy cam 10 is mounted on the camshaft 2, the mounting position of the casing 12 is determined at the rotational position where the camshaft 2 reaches the peak of the driving torque fluctuation. , And a pair of roller tappets 7 separated by 180 ° are determined so as to be located at the apexes of the dummy cam portions 20 and 21 respectively (at this time, the remaining roller tappets 7 are in contact with the base circle portion of the dummy cam 10). become.).

Therefore, the fluctuation of the driving torque of the camshaft 2 is canceled out by the fluctuation of the canceling torque in which the cycle and the amplitude change are almost the same and the directions are opposite to each other. Sound (gear noise) almost disappears.

The cylindrical casing 12 shown in FIG.
The mounting boss 22 is extended in the circumferential direction as shown in FIG. 3, and the bolt insertion hole 23 is formed as an arc-shaped long hole 23 a around the axis of the camshaft 2.
May be rotated, and the position of the roller tappet 7 with respect to the dummy cam portions 20 and 21 may be adjusted.

[0027]

As described above, according to the present invention, the following excellent effects are exhibited.

(1) Cancellation torque fluctuations having substantially the same cycle and magnitude as the driving torque fluctuation can be applied in reverse phase to the camshaft that opens and closes the intake and exhaust valves. The phenomenon can be suppressed, and the rattle (gear noise) can be reduced.

(2) The device can be made compact, lightweight and compact.

[Brief description of the drawings]

FIG. 1 is a detailed sectional view of a main part of a valve train of a four-cycle four-cylinder engine according to the present invention, as viewed from a direction along an axial direction of a camshaft.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a diagram showing a modified embodiment.

FIG. 4 is an explanatory diagram of a cam gear train.

FIG. 5 is a diagram showing torque fluctuation (a), rotational speed fluctuation (b), and gear noise (c) generated on a camshaft of a four-cylinder four-cycle engine.

FIG. 6 is a detailed sectional view of a main part showing a conventional valve train of a four-cycle four-cylinder engine.

[Explanation of symbols]

 2 Camshaft 4 Gear train 7 Roller tappet 10 Dummy cam

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F01L 1/00

Claims (1)

(57) [Claims] 1. A valve train for a four-cycle four-cylinder engine in which a crankshaft and a camshaft for driving an intake / exhaust valve are connected by a gear train. A substantially elliptical dummy cam is coaxially attached to an end of the camshaft. A roller tappet is disposed on the outer peripheral surface of the dummy cam at 90 ° intervals in the circumferential direction so as to be movable in the radial direction and can be brought into contact with the outer peripheral surface of the dummy cam by elastic force. The cam profile is set to a profile that can cause the camshaft to generate a cancel torque variation in which the variation in the cycle and the amplitude is substantially the same as the variation in the drive torque of the camshaft, and the circumferential direction between the pair of roller tappets and the dummy cam spaced by 180 ° The relative position of the camshaft is set so that the cancel torque in the opposite phase to the drive torque fluctuation is applied to the camshaft. Valve operating device of a four-cycle four-cylinder engine to symptoms.