JPH06299825A - Lost motion assembly of variable valve timing mechanism - Google Patents

Abstract

PURPOSE:To eliminate intake air or exhaust air from being leaked even when the switching operation of a rocker arm of a variable valve timing mechanism is not complete, and also to prevent the rocker arm from interfering with the other members. CONSTITUTION:The lengths of a cylinder 26 and a piston 27 of a lost motion assembly 25' for pressing a rocker arm 7 wherein a variable valve timing mechanism for connecting or releasing a rocker shaft to/from a rocker arm oscillating around the rocker shaft according to the driving state of an engine is released to a cam is so set that the rocker arm 7 may be protruded to the bottom in jumping from the cam before interfering the other members.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lost motion assembly for a variable valve timing mechanism.

[0002]

2. Description of the Related Art In a variable valve timing mechanism, two types of cams, one for low speed and the other for high speed, having different profiles are set on a camshaft, and the low speed cam drives the valve in the low speed range and the high speed cam drives in the high speed range. It is a mechanism that switches using hydraulic pressure. The low speed cam is smaller than the high speed cam, and both valve overlap and lift are smaller.

By adopting a variable valve timing mechanism,
It is possible to improve the ease of use of the practical engine in the low speed range, that is, to improve the output tokule of the engine in the high speed range while maintaining the low speed and high torque. Various variable valve timing mechanisms have been proposed, and the applicant has previously proposed variable valve timing mechanisms as shown in FIGS. 5 to 7.

5 to 7, a variable valve timing mechanism 1 includes two intake valves 2 and 3 and a T-type rocker arm 5 integrated with rocker shafts 4 and 4'for opening and closing the intake valves 2 and 3. And low-speed rocker arm 6, high-speed rocker arm 7, and T-type rocker arm 5,
The T-type rocker arm 5 is composed of pistons 8 and 9 for connecting the low speed rocker arm 6 or the high speed rocker arm 7 and the low speed cam 14 and the high speed cam 15 provided on the cam shaft 13.

Rocker shafts 4 and 4'at both ends of the T-shaped rocker arm 5 are rotatably supported by rocker shaft journals 12 and 12 ', and oil passages provided on the journals 12' and rocker shafts 4'are provided. Piston 8 through 12'a, 4'a
Oil pressure P is applied to each oil passage of journal 12 and rocker shaft 4.
The hydraulic pressure P is supplied to the piston 9 through 12a and 4a.

The base ends of the low-speed rocker arm 6 and the high-speed rocker arm 7 are rotatably fitted onto the rocker shafts 4 ', 4 on both sides of the T-shaped rocker arm 5, respectively, and the roller bearings 10, 10 are provided at the respective tips. 11 is pivotally supported. These roller bearings 10 and 11 are brought into contact with the low speed cam 14 and the high speed cam 15, respectively, and roll. The low-speed rocker arm 6 and the high-speed rocker arm 7 are in contact with the low-speed cam 14 and the high-speed cam 15 at all times by the roller motions 10 and 11 by the lost motion assembly 25 (FIG. 7) arranged on the base end side. It

In the low speed rotation range of the engine, the piston 8 is fitted into the piston hole 6b of the low speed rocker arm 6 by the spring force of the spring 17 ', and the low speed rocker arm 6 is connected to the T-shaped rocker arm 5 to be integrated. Low speed cam
The intake valves 2 and 3 are driven by 14 via the low speed rocker arm 6 and the T-shaped rocker arm 5. At this time, the piston 9 is retracted by the spring force of the spring 17, and the high-speed rocker arm 7 is released from the connection with the T-shaped rocker arm 5 and can freely swing. The roller bearing 11 is in contact with the high speed cam 15 by the lost motion assembly 25.

In the high speed rotation range of the engine, the piston 9 is pushed out by the hydraulic pressure P against the spring force of the spring 17 and fitted into the piston hole 7b of the high speed rocker arm 7, and the high speed rocker arm 7 is T-shaped rocker arm. 5, the intake valves 2 and 3 are driven by the high-speed cam 15 through the high-speed rocker arm 7 and the T-shaped rocker arm 5 so as to be integrated. At this time, the piston 8 retreats against the spring force of the spring 17 ′ by the hydraulic pressure P, the low speed rocker arm 6 is released from the T-shaped rocker arm 5,
The roller bearing 10 abuts on the low speed cam 14 by the lost motion assembly 25 and rolls.

Further, the pistons 8 and 9 are both retracted so that T
The intake valves 2, 3 are released by releasing the low-speed rocker arm 6 and the high-speed rocker arm 7 from the mold type rocker arm 5.
Can be stopped, that is, the cylinder can be stopped.

[0010]

By the way, the switching operation between the low speed rocker arm 6 and the high speed rocker arm 7 of the variable valve timing mechanism 1 is performed by the low speed rocker arm at each base circle portion of the low speed cam 14 and the high speed cam 15. 6. When the roller bearings 10 and 11 of the high speed rocker arm 7 are in sliding contact, that is, when the low speed rocker arm 6 and the high speed rocker arm 7 are not swinging.

However, the switching operation may be incomplete at some timing and the valves 2 and 3 may start to lift. After the lift of the valves 2 and 3 starts, the connecting piston 8 or 9 suddenly becomes the piston hole 6b or 7b.
When it is pulled out and the connection with the T-shaped rocker arm 5 is released, the low-speed rocker arm 6 or the high-speed rocker arm 7
Jumps from the low speed cam 14 or the high speed cam 15 against the force of the spring of the lost motion assembly 25. If the jump amount at this time is large, the low speed rocker arm 6 or the high speed rocker arm 7 collides with the retainer 21 (FIG. 7) or the like, and the intake valves 2 and 3 are slightly opened, which leads to intake leakage. The same applies to the exhaust valve. In the worst case, there is a possibility that the roller bearings 10 and 11 of the low speed rocker arm 6 and the high speed rocker arm 7 and the retainer 21 may be damaged.

The present invention has been made in view of the above points. Even if the rocker arm switching operation is incomplete, intake leakage and exhaust leakage are eliminated, and the rocker arm does not interfere with the retainer or the like. It is an object of the present invention to provide a lost motion assembly of a variable valve timing mechanism.

[0013]

In order to achieve the above object, according to the present invention, a variable valve for connecting or disconnecting a rocker shaft and a rocker arm swinging around the rocker shaft according to an operating state of an engine. The length and the length of the cylinder and piston of the lost motion assembly that presses the rocker arm against the cam when the rocker arm of the timing mechanism is released are bottomed before they interfere with other members when the rocker arm jumps from the cam. It has a set structure.

[0014]

When the rocker arm jumps from the cam for some reason, the lost motion assembly bottoms out before the rocker arm interferes with other members. This prevents interference between the rocker arm and the retainer, valve spring, or the like. Also, damage to the rocker arm, retainer, etc. is prevented.

[0015]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The same members as those shown in FIG. 7 are designated by the same reference numerals and detailed description thereof will be omitted. In FIG. 1, the lost motion assembly 25 'is a pawl of the high speed rocker arm 7.
It is vertically arranged above 7b. This lost motion assembly 25 'includes a lost motion cylinder (hereinafter simply referred to as "cylinder") 26 as shown in FIG.
A lost motion piston (hereinafter simply referred to as "piston") 27 that is inserted and inserted into the cylinder 26, and a lost motion spring (hereinafter simply referred to as "spring") 28 that is compressed between the cylinder 26 and the piston 27. Etc.

The closed end side of the cylinder 26 is slightly reduced in diameter to form a step, and at the approximate center of the end face, a normal breathing hole through which a bolt-shaped piston lifting jig is loosely inserted when adjusting the valve clearance. Has a large-diameter breathing hole 26a, and a stopper ring 29 for preventing the protrusion of the piston 27 is fitted in an annular groove 26b provided on the inner surface of the opening end. The oil supply hole 26 is located at the center of the side surface.
c is provided so that oil is supplied between the inner peripheral surface of the cylinder 26 and the outer peripheral surface of the piston 27 for lubrication.

On the other hand, the tip 27a of the piston 27 has a substantially frustoconical shape, and a screw hole 27b having a bottom is formed in the center of the inner surface of the tip 27a. This screw hole 27b is
The diameter of the cylinder 26 is slightly smaller than that of the breathing hole 26a, and the tip of the pitsun lifting jig is screwed. The lost motion spring 28 pushes out the piston 27 so that the tip 27a is projected from the opening end of the cylinder 26. The open end 27d of the piston 27 is connected to the cylinder 26
The stepped surface 26d is opposed to and separated from the stepped surface 26d.

The lost motion assembly 25 'is
The cylinder head 50 is fitted and fixed in a hole 50a vertically formed above the claw 7d of the high-speed rocker arm 7.
Then, the tip 27a of the piston 27 is moved by the spring force of the lost motion spring 28 so that the claw 7d of the high-speed rocker arm 7 is released.
Is pressed against the upper surface of. In the high speed rocker arm 7, the roller bearing 11 is pressed against the high speed cam 15 by the spring force of the spring 28 of the lost motion assembly 25 '. As a result, the roller bearing 11 of the high speed rocker arm 7 is always brought into contact with the high speed cam 15.

The length from the opening end of the cylinder 26 of the lost motion assembly 25 to the step surface 26d and the length of the piston 27 are such that the roller bearing 11 of the high speed rocker arm 7 jumps from the high speed cam 15 to the retainer 21. The length of the open end 27d of the piston 27 abutting the step surface 26d of the cylinder 26 is set so that the lost motion assembly 25 bottom-projects before it interferes with. The same applies to the lost motion assembly of the low speed rocker arm 6 and the lost motion assembly of each rocker arm for exhaust (neither is shown).

The operation will be described below. As shown in FIG. 1, the switching operation of the high-speed rocker arm 7 is incomplete at some timing, and after the lift of the intake valves 2 and 3 starts, the piston 9 connecting the high-speed rocker arm 7 to the T-shaped rocker arm 5 is released. It is assumed that the roller bearing 11 jumps from the high speed cam 15 by suddenly coming out of the piston hole 7b of the high speed rocker arm 7. The rocker arm 7 for high speed is rotated counterclockwise in the figure with the jump of the roller bearing 11, and the pawl 7d pushes up the piston 27 of the lost motion assembly 25 'against the spring force of the spring 28.

The piston 27 moves upward while compressing the spring 28, and the opening end 27d collides with the step surface 26d of the cylinder 26 and bottoms out before the roller bearing 11 interferes with the retainer 21. This prevents the high-speed rocker arm 7 from rotating counterclockwise. As a result, the high speed rocker arm 7 prevents the roller bearing 11 from interfering with the retainer 21, the valve spring 22, or the like. The same applies to the exhaust valve. This eliminates the risk of intake leak, exhaust leak, and the like.

FIGS. 3 and 4 are for preventing the collision noise when the lost motion assembly 25 'according to the present invention bottom-ends, and FIG. 3 shows the step surface 26d of the cylinder 26. As shown in FIG.
A sound deadening member, for example, a sound deadening spring 30, is attached to the opening 27d of the piston 27 so that the sound deadening spring 30 is compressed and bottoms out. As a result, the collision sound when the bottom of the lost motion assembly 25 'is struck, that is, the bottom slam is muted.

Further, FIG. 4 shows a cylinder 27 having an opening end 27d to which a ring-shaped muffling rubber 31 is fixed as a muffling member.
The piston 27 comes into contact with the step surface 26d of the cylinder 26 via the sound deadening rubber 31. This will mute the bottom strike of the lost motion assembly 25 '.

[0024]

As described above, according to the present invention, the cylinder and piston of the lost motion assembly that presses the rocker arm against the cam are caused to bottom-end before they interfere with other members when the rocker arm jumps from the cam. Since the length is set, interference between the rocker arm and the retainer, valve spring, etc. is prevented, and there is no risk of intake or exhaust leakage, and there is no risk of damage to the rocker arm or retainer, etc. This has the effect of improving the reliability of the valve timing mechanism.

[Brief description of drawings]

FIG. 1 is a sectional view of a variable valve timing mechanism to which a lost motion assembly according to the present invention is applied.

2 is an enlarged view of the lost motion assembly of FIG. 1. FIG.

FIG. 3 is a second of the lost motion assembly shown in FIG.
It is sectional drawing which shows the Example of.

FIG. 4 is a third of the lost motion assembly shown in FIG.
It is sectional drawing which shows the Example of.

FIG. 5 is an assembled perspective view of a variable valve timing mechanism using a conventional lost motion assembly.

6 is a cross-sectional view taken along the line VI-VI in FIG.

7 is a sectional view taken along the line VII-VII in FIG.

[Explanation of symbols]

 1 Variable valve timing mechanism 2, 3 Intake valve 5 T-type rocker arm 6 Low speed rocker arm 7 High speed rocker arm 8, 9 Piston 10, 11 Roller bearing 14 Low speed cam 15 High speed cam 25 'Lost motion assembly 26 Cylinder 27 Piston 28 Spring 30 silencer spring 31 silencer rubber

Claims (1)

[Claims] 1. A rocker arm of a variable valve timing mechanism for connecting or disconnecting a rocker shaft and a rocker arm swinging around the rocker shaft according to an operating state of an engine, when the rocker arm is released, the rocker arm serves as a cam. A lost motion assembly of a variable valve timing mechanism, wherein a cylinder and a piston of the lost motion assembly to be pressed are set to a length such that when the rocker arm jumps from a cam, the cylinder and the piston are bottom-butted before they interfere with other members.