JP2848683B2 - Valve train for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating device for an internal combustion engine, and more particularly to a valve operating device capable of controlling a valve lift amount and a valve opening / closing timing of an intake valve or an exhaust valve in accordance with an operating state of the engine. .

2. Description of the Related Art As is well known, for example, in a valve train of an internal combustion engine for an automobile, a plurality of intake valves are provided in one cylinder, and when the engine is running at a low speed, a part of the intake valves is closed and stopped to enhance intake swirl. To improve the combustion efficiency of the engine, while opening all the intake valves when the engine is running at a high speed to improve the output by improving the intake charge efficiency. However, in this case, a part of the intake valve is closed and stopped when the engine is running at a low speed, so that if the intake valve is in a state of being stopped for a long period of time, carbon and the like generated by combustion will cause the intake valve to stop. There is a possibility that the intake valve may stick and accumulate between the valve body and the seat portion and stick.

Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-11811, three rocker arms for low lift and high lift pivotally supported on a rocker shaft are provided with connection switching means, The two pistons of this connection switching means are appropriately moved in the axial direction by hydraulic pressure or the like so that each intake valve is always opened and closed integrally without stopping each intake valve via each rocker arm, while the relative angle of each rocker arm is controlled by the engine operation. There is also provided an apparatus that controls the lift amount and the opening / closing timing of each intake valve by displacing according to the state.

However, in the conventional example described in the above publication, for example, when switching from a state in which only one intake valve is opened and closed to a state in which both intake valves are both opened and closed,
In a section where each rocker arm slides on and rests on each base circle of the high-speed cam and the low-speed cam, the piston can be moved or switched, but the piston is started to move near the end of the base circle section. In this case, a cam lift section, that is, a rocking operation section of the rocker arm is immediately entered, and the deviation of the center axis of each guide hole starts. For this reason, the switching movement of the piston cannot be performed in time, and it is difficult to fit into the respective guide holes. Even if the engagement is slight, the fitting state is released in the middle and the reliable switching cannot be performed. As a result, there is a possibility that the piston may be repelled, causing abnormal noise or damage.

Means for Solving the Problems The present invention has been devised in view of the above-described conventional problems, and has a cam having a high-speed cam and a low-speed cam which rotate synchronously with a crankshaft of an engine and have different lift amounts. Shaft and
A plurality of rocker arms whose base ends are swingably supported by a rocker shaft, and which open an intake valve or an exhaust valve with the rotation of the selected cam, and guides provided on opposite sides of each of the rocker arms. A connecting means for appropriately connecting the rocker arms by a piston sliding in the hole via hydraulic pressure, a concave portion formed in a base circle immediately before a high-order portion of the high-speed cam, and the one rocker arm swingably. A timing lever that is rotatably supported, one end of which abuts against the outer peripheral surface of the high-speed cam including the recess, and the other end of which controls or cancels the movement of the piston, wherein the timing lever abuts the recess. The movement of the piston is restricted at the set position.

According to the present invention having the above-described structure, each rocker arm can be switched to the guide hole of the piston during the base cycle of each cam, but immediately before shifting from the base circle to the higher position, that is, the base circle is moved. Even if the hydraulic pressure for switching is supplied just before the end, at this time one end of the timing lever is located in the recess of the high-speed cam and swings in a predetermined direction, and the other end reliably restricts the movement of the piston. .
Therefore, incomplete fitting of the piston into the guide hole immediately before the lift of the high-speed cam is prevented.

On the other hand, the timing lever swings in the opposite direction in the base circle region other than the high-order portion (lift region) and the concave portion of the high-speed cam to release the movement restriction of the piston.

Embodiment An embodiment of the present invention will be described below in detail with reference to FIGS. This embodiment is applied to an internal combustion engine equipped with two valves having the same function for one cylinder (either an intake valve or an exhaust valve, and the illustrated one is an intake valve). Is shown.

That is, each cylinder is provided with a single main rocker arm 1 corresponding to the two intake valves 3, 3 urged in the valve closing direction by the valve springs 3a, 3a. The end 1a is swingably supported by the cylinder head via a main rocker shaft 4 common to each cylinder, while the tip 1b abuts the stem top of the intake valves 3,3. The main rocker arm 1 has a substantially rectangular shape in plan view, has a rectangular opening 5 cut out in the longitudinal direction of one side, and has an area larger than that of the opening 5 in the longitudinal direction of the other side. A large rectangular hole 6 having a substantially stepped rectangular shape is cut out. An elongated cutout hole 7 is formed on the base end 1a side of the rectangular hole 6 and on the outer side near the opening 5.

In the opening 5, a roller 10 is rotatably provided on a shaft 8 via a needle bearing 9 as shown in FIG. 5, while the sub rocker arm 2 is disposed in the rectangular hole 6. . In addition, the roller 10 has a low-speed cam 12 provided on a camshaft 11 that rotates synchronously with a crankshaft (not shown) in rolling contact therewith.

The base end of the sub rocker arm 2 is swingably supported by the main rocker arm 1 via a sub rocker shaft 13 as shown in FIG.
No low-speed cam 1 at the end
Cam follower part 1 that slides in contact with high-speed cam 14 arranged side by side with 2
5 is formed so as to project in an arc shape, and a lost motion spring 16 for pressing the cam follower portion 15 against the high-speed cam 14 is provided below the lower portion. The sub rocker shaft 13 is slidably inserted into an insertion hole 2a formed inside the base end of the sub rocker arm 2, and both ends of the sub rocker shaft 13 are located at opposite positions of the rectangular hole 6 of the base end 1a. It is press-fitted and fixed in the drilled press-fit holes 17,17.

Further, the main rocker arm 1 is integrally formed with a columnar concave portion 18 which is located immediately below the sub rocker arm 2 and has a lost motion spring 16 interposed therebetween. The lower end of the coil-shaped lost motion spring 16 is seated on the bottom plate 18a of the concave portion 18, and the upper end thereof is connected to a follower portion 20 formed integrally with the sub rocker arm 2 via a retainer 19 which is slidably fitted in the concave portion 18. Abut

Further, connecting means 21 between the main rocker arm 1 and the sub rocker arm 2 as shown in FIGS.
Is provided. That is, a bottomed cylindrical first guide hole 22 is formed in the width direction in the side portion of the roller 10 of the main rocker arm 1, and the first guide hole 22 is formed in the outer wall 1 c on the side of the rectangular hole 6. Third guide hole 24 having the same diameter on the same axis
Are formed. On the other hand, on the base end side of the sub rocker arm 2, a second guide hole 23 having the same diameter as that of each of the guide holes 22 and 24 is formed to penetrate in the width direction. In each of the guide holes 22, 23, 24, first, second, and third pistons 25, 26, 27 are slidably provided, respectively.
The pistons 25 and 26 are set to have the same length as the lengths of the corresponding guide holes 22 and 23, and the third piston 27 has the third length to ensure the movement of the pistons 25 and 26. The length is set shorter than the length of the guide hole 24. An oil chamber 28 is defined behind the first piston 25, and a return spring 29 for urging each of the pistons 25 to 27 toward the oil chamber 28 behind the third piston 27 is provided via a retainer 30. It is armed. The first piston 25 has an annular second engagement groove 25a formed substantially in the center of the outer peripheral surface, while the second piston 25 has a second engagement groove 25a.
The piston 26 has an annular first engagement groove 26a formed on an outer periphery of a protruding portion provided at an end portion abutting on the first piston 25.

The first piston 25 and the second piston 26 are respectively operated by the first and second guide holes 22 and 2 by the operating oil pressure guided into the oil chamber 28.
The rocker arms 1 and 2 are integrally connected by fitting over the third and third and third guide holes 23 and 24. On the other hand, when the operating oil pressure is not introduced into the oil chamber 28, the third piston 27 is pressed by the spring force of the return spring 29, and the first and second pistons 25 and 26 are moved to the first and second guide holes 22, The connection between the two rocker arms 1 and 2 is released in a state where the arm is housed in the inside 23.

A hydraulic circuit 31 for guiding the operating oil pressure to the oil chamber 28 includes an oil gallery 32 formed in the inner axial direction of the main rocker shaft 4 and a radial direction of the main rocker shaft 4 and the main rocker arm 1 as shown in FIG. Oil chamber through the interior
An oil passage 33 communicates with the oil gallery 32 and the oil gallery 32.

The oil pressure of the oil pump is guided to the oil gallery 32 via a switching valve (not shown) during a predetermined high-speed operation.
The control unit that electronically controls the operation of the switching valve
Input the engine rotation signal, cooling water temperature signal, lubricating oil temperature signal, supercharger intake pressure signal, throttle valve opening signal, etc., and suddenly fluctuate engine torque based on these detected values. Low-speed cam 12
The switching between the high-speed cam 14 and the high-speed cam 14 is performed smoothly.

The low-speed cam 12 and the adjacent high-speed cam 14 are formed in different shapes (including similar shapes having different sizes) so as to satisfy the valve lift characteristics required when the engine is running at a low speed and at a high speed. Have been. That is, the high-speed cam 14
Has a profile that makes at least one of the valve lift amount and the valve opening period larger than the low-speed cam 12. Here, the valve lift and the valve opening period are both increased.

The high-speed cam 14 has a concave portion 34 formed between the base circle 14a in the rotation direction (the direction of the arrow) and the high portion 14b, that is, at the side edge immediately before the high portion 14b of the base circle 14a. The concave portion 34 is formed by cutting out a predetermined length in the circumferential direction of the base circle 14a, and both end portions 34a and 34b are formed in a gentle slope to smoothly slide the timing lever 40 described later. .

Further, a timing lever 40 for regulating and releasing the movement of each of the pistons 25, 26, 27 is provided in the notch hole 7 of the sub rocker arm 2. This timing lever 40
As shown in FIGS. 2 (A) and 2 (B), a side portion of the sub rocker arm 2 is formed by bending the sub rocker shaft 13 through a fulcrum hole formed in the substantially L-shape. One end 40a, which is bent outward in an inclined manner, protrudes from the cutout hole 7 and is disposed on the concave portion 34 side of the high-speed cam 14, while the other end 40b is With the swinging, it selectively engages in the engagement grooves 25a and 26a. Further, the timing lever 40 is driven by the second force by the torsion spring 41 wound around the sub rocker shaft 13.
The counterclockwise direction in the drawing, that is, the upper edge of one end 40a is the high-speed cam 1
The other end 40b is constantly in contact with the outer peripheral surface including the four concave portions 34 and the other end 40b is urged toward the outer peripheral surfaces of the pistons 25 and 26.

 Hereinafter, the operation of the present embodiment will be described.

During low-speed operation of the engine (when the operating oil pressure is not introduced into the oil chamber 28), the main rocker arm 1 swings according to the profile of the low-speed cam 12, and the intake valves 3, 3 are opened and closed. At this time, although the sub rocker arm 2 is swung by the high-speed cam 14, the pistons 25, 26, 27 are respectively housed in the guide holes 22, 23, 24 by the spring force of the return spring 29, and the main rocker arm 1 is moved. Does not hinder the movement of
That is, each of the pistons 25, 26, and 27 allows independent rocking of each of the rocker arms 1 and 2 while sliding their respective opposing end surfaces against each other. On the other hand, at this time, the timing lever 40
Swings in accordance with the profile of the high-speed cam 14 via one end 40a, and in the lift region of the base circle 14a and the high-order portion 14b, the other end 40b is connected to the first engagement groove 26a as shown in FIG. And the engagement is released, but in the region of the outer peripheral surface of the concave portion 34, it is engaged in the first engagement groove 26a as shown in FIG. 2 (B) and FIG. 3 (A). Oscillating repeatedly.

On the other hand, when the engine shifts to high-speed operation, that is, for example, when the operating oil pressure is guided to the oil chamber 28 through the oil gallery 32 and the oil passage 33 in a certain region immediately before the lift of each of the cams 12, 14, each of the pistons 25 to 27 is the right direction in FIG. 3A against the spring force of the return spring 29 (toward the third guide hole 24).
However, at this time, since the one end 40a is located in the concave portion 34 and the other end 40b is engaged in the first engagement groove 26a as described above, each of the pistons 25 to 27 Movement is reliably regulated. Accordingly, the rocking operation of each rocker arm 1 and 2 which starts immediately from such a time, that is, each guide hole 2
Incomplete fitting of the pistons 25 to 27 due to the start of displacement of the central axes 2 to 24 is reliably prevented.

At the time when the one end portion 40a immediately shifts to the high portion 14b after passing through the concave portion 34, the other end portion 40b is connected to the first engagement groove 26a.
(FIG. 2 (A)), but at this point, since the center axes of the guide holes 22 to 24 are shifted,
The movement of the pistons 25 to 27 is still restricted.

Thereafter, both rocker arms 1 and 2 become stationary on the base circle of each cam 12 and 14 so that the center axes of the guide holes 22 to 24 coincide with each other, and the other end 40b of the timing lever 40 is also connected to the first engagement groove 2.
Since the state separated from 6a is continued, the movement of the pistons 25 to 27 is allowed only at this time. Therefore, the first and second pistons 25, 26 are fitted into the respective guide holes 22, 23, 23, 24 at the positions shown in FIG.
1 and 2 are connected together. This makes both rocker arms 1,2
Swings together according to the profile of the high-speed cam 14,
Each of the intake valves 3, 3 has a large opening angle and a large lift due to the lift characteristics of the high-speed cam 14, so that the intake charging efficiency and the output torque can be improved. In this state, the timing lever 40 repeatedly engages and separates from the second engagement groove 25a in accordance with the rotation of the high-speed cam 14, as shown in FIG. 3 (B).

Further, when the engine shifts from the high rotation range to the low rotation range again, the supply of the working oil pressure to the oil chamber 28 is shut off by a switching valve (not shown) and the pistons 25 to 27 are returned by the return spring.
While the rocker arms 1 and 2 are trying to move to the left with the spring force of 29, they are fixed by the force of the center axes of the guide holes 22, 23 and 24 in the direction of misalignment while the rocker arms 1 and 2 are swinging. Immediately before the lift, the movement is restricted by the other end 40b of the timing lever 40 as shown in FIG. 3 (B). As described above, the leftward movement of the pistons 25 to 27 is allowed at the base circle position immediately after the end of the lift of each of the cams 12 and 14, and the pistons 25 to 27 move to the original positions shown in FIG. The connection between 1 and 2 is released.

Further, in this embodiment, since the sub rocker arm 2 is connected to the main rocker arm 1 via the sub rocker shaft 13, the size of the sub rocker arm 2 can be reduced, and the inertial mass of the valve train can be further reduced. Valve followability in the rotation range can be improved. Further, the urging force of the lost motion spring 16 can be reduced, and the friction at the sliding contact portion between the sub rocker arm 2 and the high speed cam 14 can be reduced to reduce the fuel consumption of the engine. Roller 10 and cam follower
The mounting accuracy between 15 can be checked when assembling to the cylinder head.

In the above embodiment, the case where the present invention is applied to the intake valve is shown, but it goes without saying that the present invention can be applied to the exhaust valve. It is also possible to arbitrarily change the lift start timing of the high-speed cam and the low-speed cam, that is, the valve opening timing.

Advantageous Effects of the Invention As is apparent from the above description, according to the present invention, in particular, a recess is formed in the base circle immediately before the high-order portion of the high-speed cam, and the timing lever is pivotally supported by one rocker arm so as to be swingable. One end is in contact with the outer peripheral surface of the high-speed cam including the recess, and the movement of the piston is regulated or released by the other end of the timing lever. The movement of the piston is performed at a position where the timing lever abuts the recess. , The incomplete fitting of the piston into the guide hole immediately before the cam lift is reliably prevented, and the switching movement can always be reliably performed. As a result, it is possible to prevent the piston from being repelled due to incomplete fitting of the piston, generating abnormal noise, or being damaged.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a valve train according to the present invention, FIG. 2 (A) is a sectional view taken along the line II-II of FIG. 1, and FIG. FIG. 3 (A) is a sectional view taken along the line III-III of FIG. 1, FIG. 3 (B) is a sectional view taken along the line III-III of FIG. 1, and FIG. 4 is FIG. 5 is a sectional view taken along line IV-IV of FIG. 1, and FIG. 5 is a sectional view taken along line VV of FIG. 1 ... Main rocker arm, 2 ... Sub rocker arm,
3 ... intake valve, 4 ... main rocker shaft, 11 ... camshaft, 12 ... low speed cam, 13 ... sub rocker shaft, 14 ... high speed cam, 14a ... base circle, 14b
... high section, 21 ... connecting means, 22-24 ... guide hole, 25
27 to ... piston, 34 ... recess, 40 ... timing lever, 40a ... one end, 40b ... other end.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-31610 (JP, A) JP-A-63-124817 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 13/00 301 F01L 13/00 302

Claims (1)

(57) [Claims] A camshaft having a high-speed cam and a low-speed cam which rotate synchronously with a crankshaft of an engine and have different lift amounts, a base end portion of which is swingably supported by a rocker shaft; A plurality of rocker arms that open the intake valve or the exhaust valve with the rotation of the cam, and the rocker arms are appropriately connected by pistons that slide via hydraulic pressure in guide holes provided on opposite sides of each rocker arm. Connecting means, a concave portion formed in a base circle immediately before a high-order portion of the high-speed cam, and a pivotally supported by the one rocker arm, one end of which is provided on the outer peripheral surface of the high-speed cam including the concave portion. A timing lever that abuts and restricts or releases the movement of the piston at the other end, and moves the piston at a position where the timing lever abuts the recess. A valve gear of an internal combustion engine, characterized in that as win.