JPH0486311A - Valve system of four-cycle engine - Google Patents

Abstract

PURPOSE:To improve an output within a wide engine speed range by rotating a rocker shaft by a specified angle while rotating an eccentric large diameter part, and thereby varying positions of cam floor faces of second and third rocker arms in respect to the cam floor face of a first rocket arm. CONSTITUTION:Respective rocker arms 7 to 9 are arranged below a cam shaft 6 which has a low speed cam 3, an intermediate speed cam 4 and a high speed cam 5 arranged on both sides thereof. Respective supporting portions 7a to 9a are fitted to a rotatable rocker shaft 11. The supporting portions 8a, 9a are supported by means of large-diameter eccentric bushes 12, 13 which are fixed to the rocker shaft 11 by means of escape preventive pins 10. The rocker shaft 11 is rotated through the meshing of a rack 16 provided on a piston reciprocated by a hydraulic cylinder 15 and a pinion 17 formed on one end of the rocker shaft 11. The second and third rocker arms 8, 9 superposed on the branched end of the first rocker arm 7 are prevented from floating by a play adjusting screw 22.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is a four-stroke engine that can change the lift amount and opening timing of intake and exhaust valves according to the operating conditions. The present invention relates to a valve train, and more particularly to a valve train for a four-stroke engine that prevents the occurrence of hammering sounds that may occur between a rocker arm that is not driven by a cam and is in a floating state and a cam.

(Prior Art) Generally, in a four-stroke engine installed in vehicles such as automobiles and motorcycles, intake and exhaust valves are arranged on three sides of the combustion chamber, and these valves are driven by a valve train. . That is, the valve operating device includes a camshaft that is interlocked with the crankshaft of the engine, and uses a cam formed on the camshaft to move the intake and exhaust valves up and down at predetermined timing.

(Problems to be Solved by the Invention) By the way, the above-mentioned 4-cycle engine has the ability to obtain high output within a wide rotation speed range from low rotation speed to medium and high rotation speed, that is, has a wide power band. is desirable.

However, in conventional valve train systems, the valve opening/closing timing and lift amount are fixed, so output characteristics that only have a peak value in a specific engine speed range can be obtained, and therefore the output characteristics in the low engine speed range cannot be obtained. You are forced to choose whether to focus on the engine or the output characteristics in the medium and high rotation speed range.

This invention was made in consideration of the above-mentioned circumstances, and it is possible to improve the output within a wide rotation speed range, and it also uses a cam that does not drive the rocker arm and a rocker arm that is not driven by the cam and is in a floating state. It is an object of the present invention to provide a valve train for a four-stroke engine that can prevent the occurrence of hammering noise that may occur during engine operation.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a rocker shaft that is rotatably supported and has an eccentric large diameter portion, and a rocker shaft that is directly inserted into the rocker shaft and has a branched tip portion. 1 rocker arm, second and third rocker arms disposed on both sides of the first rocker arm and fitted into the eccentric large diameter portion, and the first, second and third rocker arms, respectively. first, second and third cams, the second and third cams are formed with the same cam profile, and the cam profile of the first cam is formed different from the cam profile; Further, the tip of one of the second and third rocker arms overlaps one of the branched tips of the first rocker arm, and
The tip of the other of the rocker arms overlaps below the other of the branched tips, and the supporting part of the second or third rocker arm overlaps the branched tip and the support of the first rocker arm. A screw for play adjustment is provided on one side of the play adjustment screw, a screw receiving part is formed on the other side, and the clearance between the tip of the play adjustment screw and the screw receiving part is configured to be adjustable. It is.

(Function) Therefore, according to the valve operating system for a four-stroke engine according to the present invention, by rotating the rocker shaft by a predetermined angle and rotating the eccentric large diameter portion, the cam floor surfaces of the second and 30th lever arms are rotated to the first position. 10 The position can be changed vertically relative to the cam floor surface of the arm.

At this time, when the cam floor surfaces of the second and 30th claw arms are moved downward relative to the cam floor surface of the 10th claw arm, the contact between the second and 30th claw arms and the second and third cams is released, The tenth lever arm and the first cam come into contact with each other, and the valves of the four-stroke engine are driven by the first cam.

Further, when the cam floor surfaces of the second and 30th claw arms are moved in three directions or to the same position relative to the cam floor surface of the first rocker arm, the contact between the 10th claw arm and the first cam is released; 2nd and 30th
The lever arm contacts the second and third cams, respectively, and the valves of the four-stroke engine are operated by the second and third cams. By rotating the rocker shaft and selecting the cam in this manner, the engine output can be balanced over a wide range of rotational speeds.

Further, the second or thirtieth claw arm, which overlaps under the branched tip of the tenth claw arm, is prevented from floating by the first rocker arm. Further, the second or thirtieth claw arm, which overlaps the branched tip of the tenth claw arm, is prevented from floating due to contact between the play adjusting screw and the screw receiving portion. For these reasons, it is possible to prevent the occurrence of hitting sounds that may occur between the cam that is not driving the rocker arm and the rocker arm that is not driven by the cam and is in a floating state.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a perspective view showing an embodiment of a valve train for a four-stroke engine according to the present invention, and FIG. 2 is a plan view of the valve train shown in FIG.

This valve train is disposed on an intake side and an exhaust side of one cylinder of an engine, respectively. The valves 1 and 2 shown in FIGS. 1 and 2 are therefore arranged for intake or exhaust.

This embodiment includes a low-speed cam 3 as a first cam, a medium-high speed cam 4 as a second cam, and a third cam disposed on one side and the other side of the low-speed cam 3, respectively. A camshaft 6 (FIGS. 3 to 6) having a cam 5 for medium and high speeds, a rocker arm 7 for low speeds as a tenth arm located below each of the cams 3, 4, and 5, and a rocker arm 20 for low speeds. A rocker arm 8 for medium and high speeds as a lug arm, a rocker arm 9 for medium and high speeds as a 30th lug arm, and these rocker arms 7.8
and a rocker shaft 11 into which the supporting parts 7a, 8a, and 9a of 9 are fitted and rotatably supported by a bearing part (not shown).

The tip of the rocker arm 7 for low speeds is branched into two directions, and one of these branched tips 7b' is superimposed on the tip 8b of the rocker arm 8 for medium and high speeds, and the other branched tip 7b is overlapped with the stem head of the valve 2. It is in contact with the part. Further, the support portion 7a of the low-speed rocker arm 7 is directly fitted onto the rocker shaft 11- and is rotatably provided.

The support portion 8a of the medium/high speed rocker arm 8 is rotatably fitted into the rocker shaft IJ- via an eccentric bushing 12 having a larger diameter than the rocker shaft 11. As shown in FIGS. 3 and 4, this eccentric bushing 12 has axes P and P' eccentric from the center 0 of the rocker shaft 11, and is removably fixed to the rocker shaft 11 by a retaining pin 10. . Therefore, this eccentric bushing 12 functions as an eccentric large diameter portion of the rocker shaft 11.

Here, the axis P of the eccentric bushing 12 is the thick top portion 12a.
is the shaft center in the low engine speed range when the thick-walled top portion 12a is located diagonally forward (Fig. 3), and the shaft center P' is the shaft center in the engine medium to high speed range when the thick walled top portion 12a is located diagonally backward (Fig. 4). This is the axis of

Further, as shown in FIGS. 5 and 6, the support portion 9a of the medium/high speed rocker shaft 9 also has an eccentric bushing 1 having the same shape as the eccentric bushing 12 and eccentric in the same direction.
3, it is rotatably fitted into the rocker shirt 11-. This eccentric bush 13 is also removably fixed to the rocker shaft 11 by a retaining pin 10, and functions as an eccentric large diameter portion.

Further, the lower surface of the distal end 9a of the medium/high speed rocker arm 9 is brought into contact with one branched distal end 7b of the low speed rocker arm 7 via a shim 1.4a. Further, the lower surface of the other branched tip 76' of the low-speed rocker arm 7 is brought into contact with the tip 8b of the medium-high speed rocker arm 8 via a shim 14a. The contact points between the branch portions 7b and 7b' of the low speed rocker arm 7 and the tips 8b and 9b of the medium and high speed rocker arms 8 and 9 are set approximately on the axes of the valves 1 and 2.

Therefore, as shown in FIG. 3 and FIG. The tip 9b moves downward following the branch tip 7b due to gravity, and the tip 8b of the rocker arm 8 is forced down by the branch tip 7b'. On the other hand, when the medium and high speed cams 4 and 5 press down the cam floor surfaces 8C and 9C of the medium and high speed rocker arms 8 and 9, respectively, as shown in FIGS. Since the branch tip 7b of the rocker arm 7 is pressed down, the branch tip 7b is forcibly lowered, and the branch tip 7b'
will also be forcibly lowered.

Note that the shim 'J-4a' is a shim having a T-shaped longitudinal section, and is fitted into the branched tip 7b of the low-speed rocker arm 7 and the tip 81 of the medium-high speed rocker arm 8 from above. In addition, the valve stem heads of valves 1 and 2 are covered with a capped cylindrical shim], 4b, and this shim 1
4b, the lower surface of the branched tip 7b of the low-speed rocker arm 7 and the tip 8b of the medium-high speed rocker arm 8 abuts. These shims 14a and 14. b is used for adjusting the tappet clearance of valves 1 and 2.

Further, among the cams 3, 4 and 5, the medium/high speed cam 4
and 5 have the same cam profile, and the low speed cam 3 has a different cam profile from the cam profile of these medium and high speed cams 4 and 5. In other words,
The cam profile of the low-speed cam 3 is set so that an appropriate valve lift amount and valve opening/closing timing can be obtained when the engine is operated in a low rotational speed range. Also,
The cam profiles of the medium and high speed cams 4 and 5 are set so as to obtain a valve lift amount and valve opening/closing timing suitable for when the engine is operated in a medium and high speed range.

The above-mentioned valve lift sensitivity is the stroke length of valves 1 and 2, and corresponds to the cam lift amount. In Fig. 7, the cam profile of the low-speed cam 3 is shown by a solid line A (cam lift amount,
ffa), and the cam profiles of the medium and high speed cams 4 and 5 are shown by a broken line B (cam lift ffl i b ). As is clear from FIG. 7, the cam profiles of the medium and high speed cams 4 and 5 are set so that a larger valve lift amount can be obtained than that of the low speed cam 3.

Note that the two-dot chain line C in FIG. 7 indicates the position when the rocker shaft 11 is rotated to position the eccentric bushings 12 and thick tops 12a and 1.3a diagonally forward (see FIGS. 3 and 3). The cam profiles of the medium and high speed cams 4 and 5 in Figure 5) are shown.

By the way, as shown in Fig. 1, the rocker shaft ]-1
The rotation is performed by a hydraulic cylinder 1-5 operated by oil pressure from the engine. This hydraulic cylinder 15
A rack 16 is connected to a piston (not shown), and this rack 16 is engaged with a pinion 17 formed at one end of the rocker shaft 1-1. Further, the hydraulic cylinder 1-5 is provided with a low-speed hydraulic port 18 and a medium-high speed hydraulic port 1-9.
8°]-9, the oil pressure from the engine is selectively introduced.

When the engine speed is in the low speed range, hydraulic pressure is supplied to the low speed hydraulic port 18, the rack 16 is pulled back, the pinion 17 is rotated in the direction of arrow M, and the eccentric bushes 1-2 and 13 are As shown in the figure and FIG. 5, the thick top portions 12a and 13a are rotated so as to be positioned diagonally forward. Furthermore, when the engine speed is in the medium/high speed range, hydraulic pressure is supplied to the medium/high speed hydraulic port 19, the rack 16 is pushed out, the pinion 17 is rotated in the direction of arrow N, and the eccentric bushing 12 and 13 is the thick top portion 1.2 as shown in FIGS. 4 and 6.
a and ]-3a are rotated so that they are positioned diagonally rearward.

In this way, the rocker shaft 11 is connected to the hydraulic cylinder etc.
．． 5. 16. 1.7, the eccentric bushing 1
．． The thick-walled top portions 12a and 13a of 2.13 are always rotated on the second hand side of the rocker shaft 11 in a range from diagonally forward to diagonally rearward.

Now, especially as shown in FIG. 2, a screw receiving part 20 is integrally molded into the support part 7a of the aforementioned low-speed rocker arm 7. This screw receiving part 20 is connected to the support part 7
It extends in the direction opposite to the branch tip 7b with respect to a, and its width is the width between the support portion 7a and the path.

On the other hand, in the medium/high speed rocker arm 9 whose distal end 9b overlaps one of the branched distal ends 7b of the low speed rocker arm 7, an adjust arm 21 is integrally formed on its support portion 9a. These adjustment arms 21. is formed to extend toward the screw receiving portion 20 in a direction opposite to the tip portion 9b with respect to the support portion 9a. This adjust arm 21
An adjustment screw 22 as a play adjustment screw is screwed onto the tip of the screw, and a lock nut 23 is screwed onto the adjustment screw 22. Rocknara I・
By loosening 23 and moving the adjustment screw 22 forward and backward, the clearance between the tip of the lock nut 23 and the screw receiving part 20 can be adjusted.

When the engine is in a low speed range, the medium-high speed rocker arm 9 does not come into contact with the medium-high speed cam 4 and is in a floating state, but the upper surface of the screw receiving part 20 of the low-speed rocker arm 7 touches the bottom of the tip of the adjustment screw 22. Due to the contact, the tip 9b of the medium/high speed rocker arm 9 rotates toward the branched tip 7b of the low speed rocker arm 7, and the medium/high speed rocker arm 9 synchronizes with the movement of the low speed rocker arm 7.

In addition, when the engine is running at low speed, the rocker arm 8 for medium and high speeds is
The tip 8b is the branch tip 7 of the low speed rocker arm 7.
Since it is forcibly rotated by b', it will not be in a floating state. In this way, the occurrence of hitting noise between the medium and high speed rocker arms 8 and 9 and the medium and high speed cams 4 and 5 is prevented.

The above adjustment screw 22 and screw receiving part 20
When the thick-walled top portions 12a and 13a of the eccentric bushes 12 and 13 are diagonally forward (low engine speed range), the clearance with the eccentric bushings 12 and 13 is approximately the same as the tappet clearance, although it varies depending on the permissible amount of hitting noise. In addition, when the thick-walled top portions 1.2a and 13a are diagonally rearward (medium/high engine speed range), or when the thick-walled top portions 1.2a and 13a change diagonally from the front to the rear, the above-mentioned tappet clearance Adjust the adjustment screw 22 so that a clearance of "2" or more is secured.
The installation position of the adjusting screw 22, the distance from the rocker shaft 11, the mounting angle of the adjusting arm 21, etc. are designed. With such a design, when the thick-walled top portions 12a and 13a are diagonally rearward or change diagonally from the front to the rear, the adjustment screw 22 and the screw receiver 20 do not inhibit the state or the change thereof. do not have.

Next, the effect will be explained.

When the engine is in the low rotation speed range, the hydraulic cylinder 15
The rocker shaft 11. When it rotates in the direction of arrow El]M, the thick top portions 12a and 13a of the eccentric bushes 1-2 and 13 are located diagonally forward (FIGS. 3 and 5). As a result, the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 move downward relative to the cam floor surface 7c of the low speed rocker arm 7. Therefore, gaps are formed between the circumferential surfaces of the medium and high speed cams 4 and 5 and the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9,
As a result, the medium and high speed cams 4 and 5 idle.

Also, at this time, the low-speed rocker arm 7 is constantly pushed upward about the axis of the rocker shaft 11 by the urging force of the valve spring 27, so that its cam floor surface 7C comes into contact with the circumferential surface of the low-speed cam 3. come into contact with Therefore, when the camshaft 6 rotates, the valves 1 and 2 move up and down based on the lift characteristic A of the low-speed cam 3 shown in FIG. That is, valves 1 and 2 open and close the combustion chamber while ensuring a valve reflux amount suitable for a low engine speed range.

On the other hand, when the rocker shaft 11 rotates in the direction of arrow N due to the operation of the hydraulic cylinder 15 when the engine is in the medium/high rotation range, the thick-walled top portions 1-2a and 1°3a of the eccentric bushes 12 and 1-3, respectively. is located diagonally backward (Figures 4 and 6). As a result, the cam floor surfaces 8C and 9C of the rocker arms 8 and 9 for medium and high speeds are moved to the road force or the same position relative to the cam floor surface 7C of the rocker arm 7 for low speeds, and the cam floor surfaces 8c and 9c are contact with the circumferential surfaces of the cams 4 and 5.

Here, as shown in FIG. 7, the medium and high speed cams 4 and 5 are formed to have a larger cam lift amount than the low speed cam 3, so under the conditions shown in FIGS. 4 and 6, the camshaft 6 is rotated, the low speed cam 3 idles, while the medium and high speed cams 4 and 5 open the valves 1 and 2 via the medium and high speed rocker arms 8 and 9, respectively, based on the lift characteristic B in FIG. to drive. As a result, valve 1
- and 2 open and close the combustion chamber while ensuring a valve lift amount suitable for the medium and high engine speed range.

According to the above embodiment, the low speed cam 3 has a cam profile suitable for the low engine speed range, and the medium and high speed cams 4 and 5 have cam profiles suitable for the medium and high engine speed range. Further, the rocker arms 8 and 9 for medium and high speeds are rotatably fitted into the eccentric bushes 12 and 1-3 of the rocker shaft 11, and the rocker arm 7 for low speeds is directly fitted and inserted into the rocker shaft 11, and the rocker shaft 11 is rotated. The contact between the low speed cam 3 and the low speed rocker arm 7, and the contact between the medium and high speed cams 4 and 5 and the medium and high speed rocker arms 8 and 9 can be selected by adjusting the valve movement. It can be selectively driven by the cam 3 or the medium and high speed cams 4 and 5. Therefore, the output of the 4-cycle engine can be improved over a wide engine speed range from a low engine speed range to a medium/high engine speed range.

Further, since the selection of the low speed cam 3 and the medium and high speed cams 4 and 5 is carried out by rotating the eccentric bushings 12 and 13, no large stress is generated in each part when selecting the cams 3, 4.5. For this reason, cam 3. 4. 5
can be selected smoothly.

Furthermore, in the low engine speed range, the cam floor surface 7C of the low speed rocker arm 7 is pushed by the low speed cam 3 and is in an operating state, but the medium and high speed rocker arms 8 and 9 are in an inactive state. However, among these, the rocker arm 8 for medium and high speeds has a branch tip 7b' of the rocker arm 7 for low speeds.
It is forced to rotate by being pushed by and moves in synchronization with this low speed cam 7, so it is not in a floating state. On the other hand, at this time, the medium/high speed cam 9 moves synchronously with the low speed rocker arm 7 due to the contact between the adjustment screw 22 and the screw receiving portion 20 . For these reasons, the medium and high speed rocker arms 8 and 9 do not float in the low engine speed range, and the medium and high speed rocker arms 8 and 9 and the medium and high speed cams 4 and 5
It is possible to prevent the occurrence of hitting sounds.

In addition, in the high speed range of the engine, the cam floor surface 8C of the medium and high speed rocker arm 8 and the cam floor surface 9C of the medium and high speed cam 9 are pushed by the medium and high speed cams 4 and 5, respectively, and are in the operating state. The rocker arm 7 is in an inactive state. However, at this time, the tip 9b of the medium/high speed rocker arm 9 presses the branched tip 7b of the low speed rocker arm 7, causing the low speed rocker arm 7 to move synchronously with the medium/high speed rocker arm 9. Since both 8 and 8 move synchronously, the low speed rocker arm 7
It is possible to prevent the occurrence of hitting noise between the cam 3 and the low speed cam 3.

Also, since the hammering noise between the medium and high speed rocker arms 8 and 9 and the medium and high speed cams 4 and 5 as well as the hitting noise between the low speed rocker arm 7 and the low speed cam 3 are prevented, these medium and high speed rocker arms 7. 8 and 9 and the cams 3.4 and 5, these low speed rocker arms 7
It is also possible to improve the durability of the rocker arms 8 and 9 for medium and high speeds, the cams 3 for low speeds, and the cams 4 and 5 for medium and high speeds.

In both of the above embodiments, the cam profiles of the medium and high speed cams 4 and 5 are as shown by the broken line B in FIG. 7, but the cam profiles of the medium and high speed cams 4 and 5 are Broken line B' in the figure or broken line B' in Fig. 9
The lifts of valves 1 and 2 during medium and high engine speeds may be changed as shown in FIG.

Further, in the above embodiment, a case has been described in which the hydraulic cylinder 15 is used as the rotational drive source for the rocker shaft 11, but a motor is used as the rotational drive source, and the rocker shaft is transmitted by power transmission means such as a pulley and a belt]-1
It is also possible to drive the rotationally.

Furthermore, in both of the above embodiments, the screw receiving part 20 is formed on the support part 7a of the rocker arm 7 for low speed, and the adjustment arm 21 is formed on the support part 9a of the rocker arm 9 for medium and high speed. rocker arm 7
An adjustment arm 21 is formed on the support portion 7a of the rocker arm 9 for medium and high speed use, and a screw receiving portion 2 is formed on the support portion 9a of the rocker arm 9 for medium and high speeds.
0 may be formed, respectively, so that the upper tip of the adjusting screw 22 comes into contact with the lower surface of the screw receiving part 20.

〔Effect of the invention〕

As described above, according to the valve train for a four-cycle engine according to the present invention, the eccentric large diameter portion is formed in the rotatably supported rocker shaft, and the second and third
Since the 0th lever arm was fitted into this eccentric large diameter portion, and the 10th lever arm was placed between the 2nd and 30th lever arms and directly fitted into the rocker shaft, the rotation of the cam due to the rotation of the rocker shaft was Depending on the selection, engine output can be improved over a wide rotational speed range.

Further, the second or thirtieth claw arm, which overlaps under the branched tip of the first rocker arm, is prevented from floating by the tenth claw arm.

Further, the second or third rocker arm overlapping the branched tip of the first rocker arm is prevented from floating due to contact between the play adjustment screw and the screw receiver. In this way, the floating rocker arm that is not driven by the cam can be synchronized with the movement of the rocker arm that is driven by the cam, so that there is a gap between this floating rocker arm and the cam that does not drive the rocker arm. It is possible to prevent the occurrence of hitting sounds that may occur.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the valve train for a four-cycle engine according to the present invention, FIG. 2 is a plan view of the valve train shown in FIGS. 5th operating state diagram showing the action of the valve train as seen from the arrows ■ and ■ directions in the figure.
6 and 6 are operating state diagrams showing the action of the valve train as viewed from the directions of arrows V and ■ in FIG. 2, FIG. 7 is a diagram showing the cam profile of the cam in FIG. FIG. 9 is a diagram showing each modification of the cam profile shown in FIG. 7. 1.2...Valve, 3...Low speed cam, 4,5...
・Mid-high speed cam, 7...Low speed rocker arm, 7a・
...Low speed rocker arm support part, 7b, 7b'...
Branch tip of rocker arm for low speed, 8, 9... Rocker arm for medium and high speed, 8a, 9a... Support part of rocker arm for medium and high speed, 8b, 9b... Tip of rocker arm for medium and high speed, 11...・Rocker shaft, 12.13...
Eccentric bushing, 20... Screw receiver, 22...
- Adjustment screw, A... Cam profile for low speed cam, B... Cam profile for medium and high speed cam. Procedural Amendment (Voluntary) Date: 14/1991

Claims (1)

[Claims] A rocker shaft that is rotatably supported and is formed with an eccentric large diameter portion; a first rocker arm that is directly fitted onto the rocker shaft and has a branched tip; second and third rocker arms arranged and fitted into the eccentric large diameter portion; first, second and third cams that drive the first, second and third rocker arms, respectively; the second and third cams are formed with the same cam profile, the cam profile of the first cam is formed different from the cam profile, and any of the second and third rocker arms One tip overlaps one of the branched tips of the first rocker arm, and the other tip of the second and third rocker arms overlaps one of the other of the branched tips. The supporting portion of the second or third rocker arm and the supporting portion of the first rocker arm, which overlap with each other, overlap each other, and further, a play adjusting screw is provided on one of the supporting portion of the second or third rocker arm and the supporting portion of the first rocker arm, and a screw receiving portion is formed on the other. A valve train for a four-cycle engine, characterized in that the clearance between the tip of the play adjusting screw and the screw receiving portion can be adjusted.