JPH0454042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve train system for a multi-cylinder engine that achieves both a lightweight and compact design and noise reduction.

[Prior Art] In a conventional valve train structure, as shown in FIG. 1, the rocker shaft 1 is usually supported at both ends, with the part supporting the rocker arm 2 being supported by the rocker support 3. Like a beam,
It is supported by Rotsuka Support 3. That is, rocker supports 3 that support the rocker shaft 1 on the cylinder head 4 are arranged so as to be located on both sides of each rocker arm 2. In such a rocker arm support structure using rocker shafts with support beams at both ends, the rocker shaft 1 supporting the rocker arm 2 has high rigidity, and the seating of the valve driven by the rocker arm 2 on the valve seat follows the valve lift curve shown in Figure 3. This occurs at the constant speed section S of A (the curve when a conventional cam lift is used and there is no deflection of the valve train), and the valve collides with the valve seat at a predetermined constant speed, so the collision noise is Relatively small.

[Problems to be Solved by the Invention] However, if the rocker shaft 1 is supported by the both-end support beam structure shown in FIG. 1, the number of rocker supports 3 will increase, making the engine larger and heavier. In recent years, in order to improve fuel efficiency and reduce costs, automobile engines and valve train systems have been made more compact and lightweight. As shown in FIG. 2, it is effective to reduce the number of rocker supports 13 and to have rocker arms 12 at both ends supported by rocker shafts 11 in the form of cantilevers.

However, if the rocker arm 12 is supported by using both ends of the rocker shaft 11 as cantilever beams as shown in FIG.
Only the valves driven by the rocker shaft 1 are driven by the rocker shaft 1 compared to the valves driven by the other centrally located rocker arm 12 of the double-end supported beam structure.
The bending caused by the bending deformation of the valve became large, and there were cases where a loud noise was generated when the valve was seated on the valve seat.

The cause of this loud noise is as follows. Since the rocker arm 12 receives an upward load from the cam and the valve, the rocker shaft 11 tends to bend upward, but since the rocker shaft 11 has a cantilever structure at both ends, it becomes a support beam at both ends. The center of the rock shaft 11 moves upward by the amount of the decrease in rigidity compared to the center of the rock shaft 11, which is supported by the rock shaft 11 in the cantilever type.
The valve driven by 2 will sit on the valve seat earlier than the other valves. The cam profile of the cam is the part S where the valve seats on the valve seat.
The valve is set to have a constant speed, but the valve driven by the rocker arm 12 supported in a cantilever type is As shown in (when the deflection is large), in order to seat the valve seat quickly, the valve lift is located outside the constant speed section S of the cam, that is, the slope is steeper than the constant speed (therefore, the speed is faster). It seats on the valve seat at the curved part. (The value obtained by differentiating the valve lift with respect to time, that is, the slope of the valve lift curve indicates the valve speed, and the steeper the slope, the faster the constant speed.)
As a result, the sound of the valve colliding with the valve seat was becoming louder.

The above problems also apply to direct drive valve systems. That is, a valve that is directly driven by a cam that is supported by a cantilevered camshaft has the problem of generating abnormal noise.

The present invention aims to eliminate the problem of valve noise that occurs when making a valve train more compact and lightweight by introducing a rocker arm or cam support structure using a cantilever type rocker shaft or camshaft as described above. The purpose is to calculate the collision speed of a valve against a valve seat driven by a rocker arm supported by a cantilever-type rocker shaft or a cam supported by a cantilever-type camshaft, and The purpose is to reduce the collision speed to the valve seat of a valve driven by a cam supported by a rocker arm supported by a rocker shaft or a camshaft with a beam supported at both ends, that is, to a speed in the constant speed region. It is something to do.

[Means for Solving the Problem] In order to achieve this object, in the valve train of the multi-cylinder engine of the present invention, a cam that drives a rocker arm supported by a cantilever-type rocker shaft or a cantilever-type rocker shaft is used. A cam in which the cam lift of the valve seating portion (constant speed portion) of the cam supported by a camshaft drives a rocker arm other than the rocker arm supported by the cantilever type rocker shaft (i.e., a rocker arm supported by a both end support beam type rocker shaft); The locking arm supported by the cantilever type locking shaft is driven so that the cam lift of the cam other than the cam supported by the cantilever type camshaft is greater than the cam lift of the portion (constant speed portion) corresponding to when the valve is seated. A cam profile is set for a cam or a cam supported by the cantilever type camshaft.

[Operation] To explain the operation of the valve train configured as described above in terms of the rocker arm type, even if the center of the rocker arm support part of the rocker shaft supported in a cantilever type moves upward due to the deflection of the rocker shaft, The cam that drives the cantilever-supported rocker arm has a cam profile that increases the cam lift, thereby driving the rocker arm in a direction that compensates for the deflection of the rocker shaft, making it easier to seat the valve on the valve seat than before. can be delayed. Therefore, the seating of the valve on the valve seat, which conventionally took place at the high speed part outside of the constant speed region of the cam lift curve, has changed.
This occurs in a constant velocity region or a velocity region close to it, and the collision speed of the valve against the valve seat is reduced compared to the conventional method.

Therefore, the collision noise when the valve seats of the valves at both ends are seated is reduced to the same level as when the rocker arm is supported by a rocker shaft in the form of a support beam at both ends, and the occurrence of abnormal noise is prevented.

The operation of the direct drive type valve train is also similar to the above operation.

[Embodiment] A preferred embodiment of a valve train system for a multi-cylinder engine according to the present invention will be described below with reference to the drawings, taking a rocker arm type valve train system as an example.

FIG. 2 shows a valve train of a multi-cylinder engine according to an embodiment of the present invention. As shown in the figure, the rocker shaft 11 has rocker arms 1 at both ends.
2a is supported in a cantilevered manner. That is, with respect to the rocker arms 12a at both ends, the rocker supports 13 are arranged only on one side of the rocker arms 12a, and the rocker arms 12a at both ends are cantilevered to the rocker shafts 11 extending outward from the rocker supports 13 at both ends. It is supported in the form of The other rocker arms 12b, namely the rocker arm 12b located at the center, are supported by the rocker shaft 11 in the form of support beams at both ends. Of the 12 ROTSUKA arms, 1EX is the ROTSUKA arm for driving the exhaust valve of the first cylinder, and 1IN is the ROTSUKA arm for driving the first cylinder's exhaust valve.
The rotsuka arm for driving the intake valve of the cylinder,
2IN is the rocker arm for driving the intake valve of the 2nd cylinder, 2EX is the rocker arm for driving the exhaust valve of the 2nd cylinder, 3EX is the rocker arm for driving the exhaust valve of the 3rd cylinder, 3IN is the rocker arm for driving the exhaust valve of the 3rd cylinder. 4IN has a Rotsuka arm for driving the intake valve of the 4th cylinder, and 4EX has a Rotsuka arm for driving the intake valve of the 4th cylinder.
shows the rocker arm for driving the exhaust valve of the fourth cylinder. Further, 14 indicates a cylinder head.

FIG. 4 shows the relationship between the rocker arm 12, the cam 15, and the valve 16 at the rocker arm 12a portions at both ends. As shown in the figure, in the overhead valve type engine, a cam 15 drives a valve lifter 17, and a push rod 18 is interposed between the valve lifter 17 and one end of the rocker arm 12a. The other end of the rocker arm 12 is in sliding contact with the upper end of the valve stem portion of the valve 16. The rocker arm 12a is supported by the rocker shaft 11 at the center in the longitudinal direction, and is able to swing around the rocker shaft 11. Also, the locking shaft 11 has locking arms 12a at both ends.
It is cantilevered at the support.

FIG. 5 shows the cam profile of the cam 15 according to the invention. In FIG. 5, the cam profile of the cam 15 is a cantilever type rock shaft 1.
A cam 1 that drives the rocker arm 12a shown in 1.
Cam lift of the part corresponding to when valve 5 is seated
_Y2 is a cam that drives the rocker arm 12b supported by a rocker shaft with support beams at both ends (the cam whose cam profile is indicated by the two-dot chain line in Fig. 5).
The valve is set so that it is larger than the corresponding camshaft when the valve is seated. The above Y ₂ is shown in FIG. 6, which will be described later.

Next, the operation in the valve train of the multi-cylinder engine according to the above embodiment will be explained.

In FIG. 4, when the cam nose of the cam 15 begins to lift the valve lifter 17 upward, the rocker arm 12a receives an upward force via the push rod 18, swings around the rocker shaft 11, and pushes down the valve 16. . Valve 1
Since the opening operation of the valve 6 is performed against the valve spring 19, the rocker arm 12a receives an upward force from both the valve 16 and the cam 15. The center of the rocker shaft 11 that supports the rocker arm 12a in a cantilever type is compared to the center of the rocker shaft 11 that supports the rocker arm 12b in the form of a beam supported at both ends by the amount that the rigidity of the rocker shaft 11 is reduced by the cantilever beam. move upwards.

However, in the embodiment of the present invention, the cam lift
Since _Y2 is different from the conventional camshaft _Y1 , its valve lift curve is as shown in FIG. That is, in FIG. 6, C shows the cam lift curve when there is no deflection of the valve train when the cam having the cam lift of the embodiment of the present invention is used, and D shows the cam lift curve when the cam having the cam lift of the embodiment of the present invention is used. 2 shows a cam lift curve in the case where the valve train system has a large deflection (in the case of the rocker arm 12a in FIG. 2).
As shown in the figure, in this embodiment, the cam lift Y ₂ for the seating of the cam is increased so that Y ₂ > Y ₁ , so that the locking arm 12a of FIG. 2, where the valve train has a large deflection,
Even in the case of , as shown in valve lift curve D,
The cam will be seated at the constant speed portion S of the cam. (The seating point is the intersection of the curves C and D with the valve lift O, that is, the horizontal axis, and the intersection of the curve D with the horizontal axis is in the constant speed section S.) Therefore, the cantilever type rocker shaft 11 Even when the valve is driven in this case, the valve collision noise is similar to that of other cylinders (valve collision noise in the case of curve A in Figure 3).
become. That is, when using a conventional cam with a cam lift of Y ₁ , the collision speed (seating speed) of the valve against the valve seat was θ ₁ as shown in Fig. 3, but the cam lift of the embodiment of the present invention has a cam lift of Y ₂ . When a cam is used, the collision entrainment of the valve 16 against the valve seat 20 is θ ₂ as shown in Fig. 6, and when θ ₂ < θ ₁ , the collision speed is smaller than before, and the collision noise is as small as that of other cylinders. Become.

Incidentally, the correction of the cam profile of the cam 15 only requires correction on the order of several hundred microns at most.
Since it does not essentially affect the opening/closing amount of the valve 16, it does not require any design changes to other parts of the engine, nor does it change the intake and exhaust performance of the engine.

FIG. 7 shows test results for suppressing abnormal noise when using the valve train system of the present invention. Figure 7 A is cam 1
5 shows the sound pressure waveform before correcting the cam profile of cam 15. B shows the cam profile of cam 15 when the cam lift Y ₂ is compared to the conventional cam lift Y _1. Y ₂ = Y ₁ +
It shows the sound pressure waveform when the relationship is set to 0.1 mm, that is, the sound pressure waveform in the case of the present invention. In the figure, before cam profile correction, the cams 15 at both ends, that is, the exhaust valve of the fourth cylinder and the
The sound pressure waveform when the exhaust valve in the cylinder is seated is larger than the sound pressure waveform when the other valves are seated, but after cam profile correction, that is, when using the cam of the present invention, when the valves at both ends are seated, The sound pressure waveform is suppressed to the same level as the sound pressure waveform when the other valves are seated.

Although the above explanation took a rocker arm type valve train as an example, the same can be said for a direct drive type valve train.

[Effects of the Invention] As explained above, in the valve train of the multi-cylinder engine of the present invention, at least one of the rocker arms is supported by the cantilever portion of the rocker shaft, or at least one of the cams is supported by the cantilever portion of the rocker shaft. In a valve train of a multi-cylinder engine that is supported by the shaft, the cam that drives the rocker arm supported by the cantilever part of the rocker shaft or the cam profile of the cam supported by the cantilever part of the camshaft is used as the valve train. The lift Y ₂ of the seating part is set larger than the lift Y ₁ of the seating part of other cams to compensate for the deflection of the cam. In contrast to the case where the valve is seated in a part where the valve comes off and has a high seating speed, the present invention has the advantage that the collision speed of the valve against the valve seat can be reduced, and abnormal noise when the valve is seated can be suppressed. can get.

Therefore, the valve train and engine can be made more compact by supporting the rocker arms at both ends with cantilever-shaped rocker shafts, or by supporting some of the cams with cantilever-style camshafts. , it is possible to reduce the weight of this engine, making it more compact and lightweight.
This provides the effect of simultaneously reducing abnormal noise.

[Brief explanation of the drawing]

Figure 1 is a side view of a conventional engine valve system, Figure 2
The figure is a side view of an engine valve system in which rocker arms at both ends are supported by cantilever-type rocker shafts, including the case of the present invention. Figure 3 shows a case in which a cam with a cam lift is used before the cam profile is corrected. FIG. 4 is a sectional view of the valve train shown in FIG. 2, FIG. 5 is a front view showing the cam profile of the valve train according to the present invention, and FIG. 6 is a cam lift according to the present invention. Figures 7A and 7B are sound pressure waveform diagrams of valve seating noise before and after cam profile correction, respectively. 11...Rotsuka shaft, 12...Rotsuka arm, 15...Cam, 16...Valve, 20...Valve seat, A...Valve lift curve without valve train deflection when using conventional cam lift, B...
...Valve lift curve for large valve train deflection (when supported on a cantilever beam) when using a conventional cam lift, C
... Valve lift curve with no valve train deflection when using the cam lift of the present invention, D... Valve lift with large valve train deflection (when cantilever supported) when using the cam lift of the present invention Curve, Y ₁ ... Cam lift of conventional valve seating part (constant speed part),
Y ₂ ...(constant speed part) of the valve seating part of the present invention
cam lift, θ ₁ ...Conventional valve seating speed,
θ ₂ ... Seating speed of the valve of the present invention.

Claims (1)

[Claims] 1. In a valve operating system of a multi-cylinder engine in which at least one rocker arm or cam out of a plurality of rocker arms or cams that drive valves is supported on a cantilever shaft or a part of a rocker shaft or camshaft, The cam profile of the cam supported on the shaft of the support beam, the cam lift of the valve seating part of the cam,
The multi-cylinder is characterized in that the cam lift is set to be larger than the cam lift of a valve seating portion of a cam that drives a rocker arm supported on a rocker shaft other than a cantilevered portion or a cam supported on a camshaft other than a cantilevered portion, respectively. Engine valve system.