JP2905896B2 - Valve system for 4-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a valve train for driving an intake / exhaust valve of a four-stroke engine. The present invention relates to a valve train for a four-cycle engine that can change a lift amount, a valve opening time, and the like of an exhaust valve.

(Prior Art) As a valve train capable of changing the lift amount of an intake / exhaust valve in accordance with an operating condition, there is a device described in Japanese Utility Model Laid-Open No. 55-152308.

In this invention, two sets of two cams and two rocker arms for driving this valve are installed for one valve,
The two rocker arms are supported by a rocker shaft via two eccentric fulcrums (eccentric bushes). Then, the rocker shaft is turned according to the running condition of the engine, and one of the two
A set of rocker arms and cams are brought into contact with each other, and the valve is driven by a cam that is optimal for the operating state.

(Problems to be Solved by the Invention) In the above-described conventional example, the fulcrum (eccentric bush) where the first rocker arm rotates and the fulcrum (eccentric bush) where the second rocker arm rotates are 180 ° in opposite directions. Since the position is shifted and eccentrically mounted on the rocker shaft and integrally fixed, the amount of displacement of the rocker arm can be increased, and as a result, the cam profile can be significantly different.

However, since the above-mentioned fulcrums are integrally fixed to the rocker shaft, it is difficult to assemble the rocker arm to these fulcrums. Therefore, the maintainability of the valve gear is also reduced. Further, the workability of the rocker shaft manufactured by machining is also reduced. These assemblability, maintainability and workability are particularly remarkable in the case of a multi-cylinder engine.

The present invention has been made in view of the above circumstances, and can improve the assemblability of the rocker arm and the maintainability of the device, and can improve the workability of the four-cycle engine, which can also improve the workability of the rocker shaft. It is intended to provide a valve device.

[Configuration of the invention]

(Means for Solving the Problems) The present invention is directed to a first rocker arm for low speed, and second and third middle rockers for middle and high speeds respectively disposed on one side and the other side of the first rocker arm. A rocker arm, rotatably supported and formed with an eccentric large-diameter portion, wherein the support portions of the second and third rocker arms are fitted into the eccentric large-diameter portion;
A rocker shaft into which a support portion of the first rocker arm is directly inserted, and first, second, and third cams for driving the first, second, and third rocker arms, respectively. The second and third cams have the same cam profile, the first cam has a different cam profile from the cam profile, and the eccentric large diameter portion has a larger diameter than the rocker shaft. The first rocker arm has its tip abutted on the stem head of the valve to push down the valve, and the first rocker arm pushes down the valve. The second and third rocker arms abut against the first rocker arm, and the valve is depressed through the first rocker arm. It is an butterfly.

(Operation) Therefore, according to the valve train of the four-stroke engine according to the present invention, by rotating the rocker shaft by a predetermined angle to rotate the eccentric large-diameter portion, the medium and high speed second and third rocker arms are rotated. The position of the cam floor surface is vertically changed relative to the cam floor surface of the first rocker arm for low speed. When the cam floor surfaces of the second and third rocker arms are shifted downward with respect to the cam floor surface of the first rocker arm, the contact between the second and third rocker arms and the second and third cams is released, and the first rocker arm is released. And the first cam come into contact, and the valve of the four-stroke engine is driven by the first cam.

Further, when the cam floor surfaces of the second and third rocker arms are changed to a position substantially above or at the same position with respect to the cam floor surface of the first rocker arm, the contact between the first rocker arm and the first cam is released, and the second rocker arm is released. And the third rocker arm abuts the second and third cams, respectively.
The valves of the four-cycle engine are operated by the second and third cams.

Since the eccentric large-diameter portion of the valve gear is constituted by a detachable eccentric bush, machining of the rocker shaft is easy, and the first, second and third rocker arms are connected to the rocker shaft and the eccentric bush large diameter. It can be easily attached to the part. Further, maintainability is also improved. These improvements in workability, assemblability, and maintainability are even more remarkable in the case of a multi-cylinder engine.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a valve train of a four-stroke engine according to the present invention, FIG. 2 is a plan view of the valve train of FIG. 1, FIG. 3 and FIG. FIG. 5 is an operation state diagram showing an operation of the valve gear of FIG.

The valve train is disposed on the intake side and the exhaust side of one cylinder of the engine. Therefore, the valves 1 and 2 shown in FIGS. 1 to 4 are arranged for intake or exhaust.

This embodiment includes a low-speed cam 3 as a first cam, a middle-high speed cam 4 as a second cam disposed on one side and the other side of the low-speed cam 3, and a third cam, respectively. A camshaft 6 (FIGS. 3 and 4) also having a middle-high speed cam 5 and a low-speed rocker arm 7, 2 as a first rocker arm located below each of the cams 3, 4, and 5. A rocker arm 8 for medium and high speed as a rocker arm and a rocker arm 9 for medium and high speed as a third rocker arm, and supporting portions 7a, 8a and 9a of these rocker arms 7, 8, and 9 are fitted and provided with a bearing (not shown). Rocker shaft 11 rotatably supported
And is provided.

The tip of the low-speed rocker arm 7 branches in two directions, and these two branched ends 7b abut the stem heads of the valves 1 and 2 for opening and closing the combustion chamber of the engine (not shown). Further, the support portion 7a of the low-speed rocker arm 7 is directly inserted into the rocker shaft 11 and is provided rotatably.

The support portion 8a of the medium / high speed rocker arm 8 is rotatably fitted to the rocker shaft 11 via an eccentric bush 12 having a larger diameter than the rocker shaft 11. This eccentric bush 12
As shown in FIG. 3, the shaft center is eccentric from the center of the rocker shaft 11 and is detachably fixed to the rocker shaft 11 by a pin 10. Therefore, this eccentric bush
It functions as an eccentric large-diameter part in the rocker shaft 11 with 12 teeth.

As shown in FIG. 2, the support portion 9a of the medium / high speed rocker shaft 9 is also rotatable to the rocker shaft 11 via an eccentric bush 13 having the same shape as the eccentric bush 12 and eccentric in the same direction. Is inserted. The eccentric bush 13 also functions as an eccentric large diameter portion.

The lower end of each of the middle and high speed rocker arms 8 and 9 is connected to one and the other branch tip 7 b of the low speed rocker arm 7.
, Respectively, through the shim 14. This Sim 14
Is a shim having a T-shaped vertical cross section, which is fitted into both branch portions 7b of the low-speed rocker arm 7 from above. The contact point between the branch portion 7b of the low-speed rocker arm 7 and the tip portions 8b and 9b of the medium- and high-speed rocker arms 8 and 9 is set substantially on the axis of the valves 1 and 2.

Therefore, as shown in FIG. 3, when the low-speed cam 3 presses down on the cam floor surface 7c of the low-speed rocker arm 7 and lowers its tip 7b, the rocker arms 8 and 9 move.
Each of the tip portions 8b and 9b descends following the branch portion 7b by gravity. On the other hand, as shown in FIG. 4, when the middle and high speed cams 4 and 5 depress the cam floor surfaces 8c and 9c of the middle and high speed rocker arms 8 and 9, respectively, the tip portions 8b and 9b of these rocker arms 8 and 9 are pressed. Depresses each tip 7b of the low-speed rocker arm 7, the tip 7b is forcibly lowered.

Among the cams 3, 4 and 5, the middle and high speed cams 4 and 5 have the same cam profile,
Have different cam profiles from those of these medium and high speed cams 4 and 5. That is, the cam profile of the low-speed cam 3 is set such that a valve lift amount and an opening / closing valve timing that are appropriate when the engine is operated in a low rotation speed range. The cam profiles of the middle and high speed cams 4 and 5 are set such that an appropriate valve lift amount and opening / closing valve timing are obtained when the engine is operated at a medium / high rotation speed.

The valve lift amount is the stroke length of the valves 1 and 2, and coincides with the cam lift amount. FIG. 5 shows the cam profile of the low-speed cam 3 by a solid line A (cam lift amount).
la), and the cam profiles of the middle and high speed cams 4 and 5 are indicated by a broken line B (cam lift lb). As is apparent from FIG. 5, the cams 4 and 5 for medium and high speeds are used.
The cam profile is set so that a larger valve lift than the low speed cam 3 can be obtained.

The two-dot chain line C in FIG. 5 indicates the middle and high speed cams 4 and 4 when the rocker shaft 11 is rotated to position the tops 12a and 13a of the eccentric bushes 12 and 13 diagonally forward (FIG. 3). 5 shows the cam profile at 5.

By the way, as shown in FIG. 1, the rocker shaft 11 is rotated by a hydraulic cylinder 15 operated by hydraulic pressure from the engine. A rack 16 is connected to a piston (not shown) of the hydraulic cylinder 15.
Is a pinion 17 formed at one end of the rocker shaft 11.
To be engaged. Further, the hydraulic cylinder 15 is provided with a low-speed hydraulic port 18 and a high-speed hydraulic port 19, and hydraulic pressure from the engine is selectively guided to the respective ports 18,19.

When the engine speed is in the low speed range, the 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 0, and the eccentric bushes 12 and 13 are shown in FIG. As shown, the tops 12a and 13a rotate so as to be positioned diagonally forward. When the engine speed is in the middle / 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 turned in the direction of arrow P, and the eccentric bush 12 and As shown in FIG. 4, 13 rotates so that its tops 12a and 13a are positioned obliquely rearward.

 Next, the function and effect will be obtained.

When the engine is in the low speed range, the hydraulic cylinder 15
When the rocker shaft 11 is rotated in the direction of the arrow O by the operation of (1), the tops 12a and 13a of the eccentric pushes 12 and 13 are respectively positioned diagonally forward (FIG. 3). As a result, the cam floor surfaces 8c of the medium and high speed rocker arms 8 and 9 are formed.
And 9c move downward relative to the cam floor surface 7c of the low-speed rocker arm 7. Therefore, a gap is formed between the periphery of the middle and high speed cams 4 and 5 and the cam floor surfaces 8c and 9c of the middle and high speed rocker arms 8 and 9, and as a result, the middle and high speed cams 4 and 5 run idle. I do.

In addition, since the low-speed rocker arm n is constantly pushed upward about the axis of the rocker shaft 11 by the urging force of the valve spring 20, its cam floor surface 7c is in contact with the peripheral surface of the low-speed cam 3. Abut Therefore, when the camshaft 6 rotates, the valves 1 and 2
Moves up and down based on the lift characteristic A of the low-speed cam 3 shown in FIG. That is, the valves 1 and 2 open and close the combustion chamber while ensuring a valve lift appropriate for a low engine speed range.

On the other hand, when the rocker shaft 11 rotates in the direction of the arrow P by the operation of the hydraulic cylinder 15 when the engine is in the middle / high rotation range, the tops 12a and 13a of the eccentrics 12 and 13 are respectively positioned diagonally rearward (fourth) Figure). This allows
The cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 move relatively upward or to the same position with respect to the cam floor surface 7c of the low speed rocker arm 7, and these cam floor surfaces 8c and 9c And 5 are in contact with the peripheral surface.

Here, as shown in FIG. 5, the medium and high speed cams 4 and 5 have a larger cam lift than the low speed cam 3, so that the camshaft 6 is rotated under the condition shown in FIG. In this case, the low speed cam 3 idles, while the medium and high speed cams 4 and 5 drive the valves 1 and 2 via the medium and high speed rocker arms 8 and 9 based on the lift characteristics B in FIG. As a result, valves 1 and 2
Opens and closes the combustion chamber while ensuring a valve lift suitable for the middle and high engine speed ranges of the engine.

According to the above embodiment, a cam profile suitable for the low speed range of the engine is formed on the low speed cam 3, and a cam profile suitable for the middle / high speed range of the engine is formed on the middle and high speed cams 4 and 5. Further, the medium and high speed rocker arms 8 and 9 are rotatably fitted into the eccentric bushes 12 and 13 of the rocker shaft 11, respectively, and the low speed rocker arm 7 is directly fitted into the rocker shaft 11 to form the rocker shaft 11.
The rotation of the cam 11 and the low-speed rocker arm 7
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.
Valves 1 and 2 with low-speed cam 3 or medium-high speed cam
4 and 5 can be selectively driven. Therefore, the output of the four-stroke engine can be improved in a wide rotation speed range from the low rotation speed range to the middle and high rotation speed ranges of the engine.

Further, since the selection of the low speed cam 3 and the middle and high speed cams 4 and 5 is performed by the rotation of the eccentric bushes 12 and 13, no great stress is generated in each part when the cams 3, 4 and 5 are selected. Therefore, the cams 3, 4, and 5 can be smoothly selected.

Furthermore, since the eccentric large-diameter portion of the valve operating device is constituted by the detachable eccentric bushes 12 and 13, the rocker shaft 11 may have a cylindrical or columnar shape, and the rocker shaft 12 can be easily processed. At the same time, the low speed rocker arm 7 and the medium and high speed rocker arms 8 and 9 can be easily assembled to the rocker shaft 11 and the eccentric bushes 12 and 13, respectively. As a result, the maintainability of the valve train is also improved. Workability of these rocker shafts 11,
The improvement of the assemblability of the rocker arms 7, 8 and 9 and the maintainability of the valve train are particularly remarkable in the case of a multi-cylinder engine.

In addition, since the support portion 7a of the low-speed rocker arm 7 is directly inserted into the rocker shaft 11, the vertical position of the low-speed rocker arm 7 can always be set to a constant and appropriate position. Therefore, the branch portion 7b of the low-speed rocker arm 7 and the valve 1
And the valve clearance with the stem head can be always set appropriately. As a result, the valve clearance is optimal even at low speeds including idling, and the valve noise at this time can be reduced.

Further, since the support portion 7a of the low-speed rocker arm 7 is directly fitted to the rocker shaft 11, the rocker shaft 11 is rotated by the hydraulic cylinder 15 and held at a fixed position shown in FIG. When selecting, the turning power of the rocker shaft 11 and the holding force for holding the rocker shaft 11 at a fixed position can be reduced. Therefore, the hydraulic cylinder
Even when the hydraulic pressure supplied to 15 is low, the rocker shaft
11 can be reliably rotated and held in a fixed position.

In the above-described embodiment, the case where the cam profiles of the middle and high speed cams 4 and 5 are indicated by broken lines B in FIG. 5 has been described. However, the cam profiles of the middle and high speed cams 4 and 5 are shown in FIG. The lift of the valves 1 and 2 when the engine is running at a medium or high speed may be changed as shown by a broken line B 'in FIG. 7 or a broken line B "in FIG.

Further, in the above embodiment, the case where the hydraulic cylinder 15 is used as the rotational drive source of the rocker shaft 11 has been described. However, a motor is used as the rotational drive source, and the rocker shaft 11 is rotationally driven by power transmission means such as a pulley and a belt. You may make it do.

〔The invention's effect〕

As described above, according to the valve train of a four-stroke engine according to the present invention, the first rocker arm for low speed, and the medium and high speed ones arranged on one side and the other side of the first rocker arm, respectively. The second and third rocker arms are rotatably supported and formed with an eccentric large diameter portion. The support portions of the second and third rocker arms are fitted into the eccentric large diameter portion, and A rocker shaft into which a support portion of the first rocker arm is directly inserted, and first, second, and third cams for driving 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 differently from the cam profile, and the exciting The large diameter portion has a diameter larger than that of the rocker shaft, and the axis is constituted by a detachable eccentric bush whose axis is eccentric from the axis of the rocker shaft. The workability of the rocker shaft can be improved, and the assemblability of the first, second, and third rocker arms can be improved. As a result, the maintainability of the valve train can be improved.

Further, the first rocker arm has its tip abutting on the stem head of the valve to push down the valve, and the second and third rocker arms abut the first rocker arm, and via the first rocker arm. Since the valve is configured to be pressed down, the valve clearance between the first rocker arm and the stem head of the valve can always be appropriately set, and the valve noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a chassis diagram showing one embodiment of a valve train of a four-cycle engine according to the present invention, FIG. 2 is a plan view of the valve train of FIG. 1, and FIGS. 3 and 4 are FIG. FIG. 5 is a view showing the cam profile of the cam of FIG. 1, and FIGS. 6 and 7 are each a modification of the cam profile shown in FIG. FIG. 1,2… valve, 3… low speed cam, 4,5… medium speed cam, 7
... Low-speed rocker arm, 7a ... Low-speed rocker arm support, 8,9 ... Medium-high speed rocker arm, 8a, 9a ... Medium-high speed rocker arm support, 11 ... Rocker shaft, 12,13 ... Eccentric bush, A: Low speed Cam profile of cam for cam, B ... Cam profile of cam for middle and high speed.

Claims (1)

(57) [Claims] A first rocker arm (7) for low speed, and second and third rocker arms (8) for middle and high speed respectively disposed on one side and the other side of the first rocker arm (7). , 9) and an eccentric large-diameter portion is formed rotatably and the eccentric large-diameter portion is formed. The support portions (8a, 9a) of the second and third rocker arms are fitted into the eccentric large-diameter portion. The rocker shaft 11 into which the support portion (7a) of the first rocker arm is directly inserted, and the first, second and third driving members for driving the first, second and third rocker arms (7 to 9), respectively. Cams (3-5),
The second and third cams (4,5) are formed in the same cam profile, the cam profile of the first cam (3) is formed differently from the cam profile, and the eccentric The large-diameter portion has a diameter larger than that of the rocker shaft 11, and is constituted by a detachable eccentric bush (12, 13) whose axis is eccentric from the axis of the rocker shaft 11, while the first rocker arm ( 7) The tip (7b) abuts the stem head of the valve (1, 2) to depress the valve (1, 2), and the second and third rocker arms (8, 9) A valve operating device for a four-stroke engine, wherein the valve (1, 2) is pressed down through the first rocker arm (7).