JPH0543203Y2 - - Google Patents

Description

[Detailed description of the invention] <<Field of industrial application>> The present invention relates to an engine valve train, and in particular to an engine valve train in which cams are used to open and close intake valves depending on the engine speed. Regarding equipment.

《Prior art》 Conventionally, as this type of valve train, for example,
There is one disclosed in Publication No. 61-58605.
This valve train is an engine in which two intake valves are arranged for each cylinder, in which a camshaft is formed with a low-speed cam having a low-speed cam profile and a high-speed cam having a high-speed cam profile, A single low-speed rocker arm that transmits the movement of the low-speed cam to both intake valves is in sliding contact with the low-speed cam, and on the side of this low-speed rocker arm,
A high-speed rocker arm is disposed in sliding contact with the high-speed cam and transmits its movement to the low-speed rocker arm, and a hydraulic switching means switches the low-speed rocker arm and the high-speed rocker arm into an interlocking state or a non-interlocking state. When the engine is running at low speeds, the switching means is switched to a non-interlocked state and the intake valve is driven by the low-speed cam, while at high engine speeds, the switching means is switched to the linked side and the intake valve is driven by the high-speed cam. This opens and closes the intake valve at timings that correspond to the engine speed.

However, in this valve train, the two intake valves are actually opened and closed directly by one low-speed rocker arm at both low and high speeds, and this low-speed rocker arm is used at high speeds. Since the two intake valves are opened and closed by the high-speed rocker arm disposed on the side of the intake valve, the positional relationship of the low-speed and high-speed rocker arms and cams with respect to the two intake valves is inevitably offset asymmetrically. Put it away. For this reason, different amounts of prying force are generated on the two intake valves, increasing their sliding resistance, and a torsional moment acts on the low-speed and high-speed rocker arms. There was a problem in that uneven wear occurred on the sliding parts with the rocker shaft.

Therefore, the present applicant previously proposed in Japanese Patent Application No. 61-246084, ``Engine Valve Drive Device,'' by providing two independent low-speed Rocker arms corresponding to the two intake valves of each cylinder, and connecting them to two independent low-speed Rocker arms. In addition to slidingly contacting the low-speed cam, a high-speed rocker arm that is in sliding contact with the high-speed cam is arranged between these two low-speed rocker arms, and this high-speed rocker arm is connected to this and each low-speed rocker arm on both sides thereof. A valve train is constructed by providing a hydraulic switching means for switching between an interlocking state and a non-interlocking state, thereby making the positional relationship between the low-speed and high-speed rocker arms and cams symmetrical with respect to the two intake valves. Proposed.

<<Problems to be solved by the invention>> By the way, if the low-speed Rocker arm and the high-speed Rocker arm are engaged and disengaged depending on the engine speed, in order to prevent the high-speed Rocker arm from swinging wildly at low speeds, The high-speed rocker arm must be biased with a coil spring or the like to keep it in sliding contact with the high-speed cam at all times.

In this case, in the above proposal, three rocker arms are provided on the rocker shaft, so in terms of space, both ends of the rocker arms can be hooked between the low speed rocker arm and the high speed rocker arm to function as a torsion spring. It was not possible to install the coil spring coaxially with the Rocker shaft. Therefore, the coil spring is tensioned so that its one end is locked to the upper side of the arm on the intake valve side of the high-speed rocker arm, and the other end is extended to the exhaust valve side and locked to the cylinder head. A method was adopted to make it function as a spring.

However, in this case, the overall length of the coil spring must be made longer to cover the full range of the rocking stroke of the high-speed Rocker arm, and the spring force must be set to a certain degree to prevent resonance, so the valve train The driving resistance of the mechanism increases, and the cylinder head cover must be lifted upward to accommodate the coil spring, which increases the overall height of the engine.

The present invention was developed in view of the above circumstances, and its purpose is to reduce the driving resistance of the valve mechanism by downsizing the biasing spring of the high-speed Rotsuker arm, and to reduce the overall height of the engine. The purpose of this invention is to provide a valve train.

<Means for Solving the Problems> In order to solve the above problems, the present invention addresses the two intake valves provided per cylinder, and provides low-speed control for each intake valve and camshaft. Two low-speed rocker arms are provided so as to be able to slide freely on the rocker shaft, spanning between the cam and the rocker shaft. A high-speed rocker arm is slidably supported on the high-speed rocker arm, and the other arm of the high-speed rocker arm is equipped with a hydraulic switching means for switching the high-speed rocker arm and the low-speed rocker arms on both sides of the high-speed rocker arm into an interlocking state or a non-interlocking state. In an engine valve train equipped with a valve drive system, the high-speed rocker arm is placed between the valve-side arm of the low-speed rocker arm and the other arm of the high-speed rocker arm, and the high-speed rocker arm is always in contact with the high-speed cam. A biasing spring is provided to bring them into contact.

<<Operation>> According to the present invention having the above configuration, when the engine rotates at high speed, the high-speed rocker arm is engaged with the low-speed rocker arm by the hydraulic switching means and becomes interlocked. At this time, the intake valve is driven to open and close by the high-speed cam, and the high-speed rocker arm is brought into contact with the high-speed cam by the valve spring of the intake valve. On the other hand, when the engine rotates at low speeds, the high-speed rocker arm is separated from the low-speed rocker arm by the hydraulic switching means and is in a non-interlocked state, and the intake valve is driven to open and close by the low-speed cam. At this time, the high-speed Rotsuker arm is
A biasing spring is provided extending between the valve-side arm portion of this valve and the valve-side arm portion of the low-speed rocker arm, which abuts against the high-speed cam and prevents the rocker arm from swinging wildly. In this case, the biasing spring only needs to be able to absorb the relative difference in the rocking stroke between the high-speed Rocker arm and the low-speed Rocker arm, so it is possible to shorten its overall length and make it as compact as possible. It is now easier to install the spring between the valve-side arms of the high-speed Rotsuker arm and the low-speed Rotsuker arm, making it possible to lower the overall height of the engine and reducing the amount of energy consumed in expanding and contracting the biasing spring. By making it as small as possible, the drive resistance of the valve mechanism can be reduced.

<<Example>> Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figures 1 and 2 show an embodiment in which the engine valve train of the present invention is applied to the intake valve side of a three-valve type engine; Figure 1 is a plan view thereof, and Figure 2 is a It is a side sectional view. In the figure,
Reference numeral 1 denotes a camshaft, and the camshaft 1 is provided with three cams 2a, 2b, 3 for driving intake valves and one cam 4 for driving exhaust valves per cylinder.

Two of the three intake valve driving cams 2a, 2b, 3 are low-speed cams 2a, 2b with low-speed cam profiles, and the remaining one is a high-speed cam 3 with a high-speed cam profile. The low-speed cams 2a and 2b are arranged at both ends of each cylinder, and the high-speed cam 3 and the exhaust valve driving cam 4 are arranged between them.

A rocker shaft 5 is provided above the camshaft 1 and on the side thereof, and three rocker arms 6, 7, 8 are disposed on the rocker shaft 5 so as to be able to slide thereon. There is.

The two rocker arms provided on both sides are low-speed rocker arms 6 and 7, and the arm portions 6a and 7a at one of the swinging ends roll into contact with the low-speed cams 2a and 2b of the camshaft 1 via a roller 9. At the same time, the arm portions 6b and 7 at the other swing end
b is in contact with the valve stem 11a of the intake valve 11 via the hydraulic lash adjuster 10, and is provided so as to span approximately linearly between the low-speed cams 2a, 2b and the intake valve 11. ing. Also,
The low-speed rocker arms 6, 7 are each formed symmetrically.

On the other hand, these two low-speed Rotsuker arms 6,
The rocker arm 8 provided in sliding contact with the side surface of the camshaft 7 and between them is the rocker arm 8 for high speed use, and the arm portion 8a at the swinging end on the camshaft 1 side of the high speed rocker arm 8 is attached to the camshaft 1 by a slipper 12. is in sliding contact with the high speed cam 3.
In addition, this high-speed rocker arm 8 is attached to the arm portion 8b at the swinging end on the other valve side, and the low-speed rocker arms 6a, 6b on both sides are attached to the high-speed rocker arm 8 depending on the engine speed.
Hydraulic switching means 13 is provided for switching between an interlocking state and a non-interlocking state by engaging and disengaging the motor.

This hydraulic switching means 13 has a hydraulic chamber 14 integrally formed in the valve-side arm portion 8b of the high-speed rocker arm 8, and slides within this hydraulic chamber 14 toward the low-speed rocker arms 6 and 7. A plunger 15 that is provided so as to be retractable from the side, and a plunger 1 that is integrally formed on the low-speed rocker arms 6 and 7 corresponding to the plunger 15.
6 storage chamber 16 and a receiver 17 that is extendably provided within this storage chamber 16.
Lubricating oil whose pressure is regulated according to the engine speed by a pressure regulator (not shown) is supplied as hydraulic oil through the oil supply passage 18 from the engine.

By the way, between the valve-side arm portion 8b of the high-speed rocker arm 8 and the valve-side arm portions 6b, 7b of the low-speed rocker arms 6, 7, the high-speed rocker arm 8 is always connected to the high-speed cam. A biasing spring 20 is provided that biases the base plate 3 into contact with the base plate 3. The biasing spring 20 is a coil spring that functions as a compression spring, and one end 20a of the biasing spring 20 is seated on a seat 21 that is integrally formed on the valve-side arm portions 6b and 7b of the low-speed rocker arms 6 and 7. The end 20b is the arm part 8 on the valve side of the high-speed Rocker arm 8.
It is seated on a catch seat 22 that is integrally formed with b.

The seats 21 of the low-speed rocker arms 6 and 7 are moved from the vicinity of the hydraulic lash adjuster 10 built into the swinging ends of the valve-side arm portions 6b and 7b toward the inside of the two low-speed rocker arms 6 and 7. The high-speed Rotsuker arm 8 is extended toward the
The seat 22 of the high-speed rocker arm 8 is provided in a dish shape so as to be substantially parallel to the lower surface of the arm portion 8b on the valve side. Two cylindrical recesses are formed facing the respective seats 21 of the low-speed rocker arms 6 and 7.

Therefore, in the engine valve train configured in this manner, when the engine is running at high speed, high hydraulic pressure regulated by the pressure regulator is supplied into the hydraulic chamber 14 of the high-speed rocker arm 7, and this causes the plunger to 15 is fitted into the accommodation chamber 16 of the low-speed rocker arms 6, 7, and the high-speed rocker arm 8 engages with the low-speed rocker arms 6, 7, so that they are integrated into an interlocking state. Then, intake valve 1
1 is driven to open and close by the high-speed cam 3, and the high-speed rocker arm 8 is brought into contact with the high-speed cam 3 by the urging force of the valve spring 23 of the intake valve 11.

On the other hand, when the engine is running at low speed, the pressure of the lubricating oil supplied into the hydraulic chamber 14 by the pressure regulator is reduced, and the plunger 15 is pushed back into the hydraulic chamber 14 by the return spring 17a of the receiver 17. This allows high-speed Rotsuker arm 8
is detached from the low-speed rocker arms 6 and 7, and these become uncoupled. Then, the two intake valves 11 are driven to open and close by the low-speed cams 2a and 2b, and at this time, the high-speed rocker arm 8 is brought into contact with the high-speed cam 3 by the biasing spring 20 to prevent its rampage. is prevented.

By the way, when the biasing spring 20 is provided across the high-speed rocker arm 8 and the low-speed rocker arms 6 and 7 and used as a so-called rains spring, the amount of expansion and contraction is equal to the swing stroke of the high-speed rocker arm 8 and the low-speed rocker arm 6, 7. 6 and 7 (i.e., the difference in lift curve due to the difference in the shape of the cam profile between the high-speed cam 3 and the low-speed cams 2a and 2b), it is sufficient that the biasing spring By shortening the length of 20, miniaturization can be achieved as much as possible. As a result, the biasing spring 2
Since the amount of energy expended in the expansion and contraction of the valve mechanism is reduced, the driving resistance of the valve mechanism can be reduced. , 7 arm part 6 on the valve side
b, 7b, and the height of the cylinder head cover (not shown) can be lowered to reduce the overall height of the engine.

In addition, when the biasing spring 20 is arranged as a rain spring between the high-speed rocker arm 8 and the low-speed rocker arms 6 and 7, the spring force is equal to the acceleration of the high-speed cam 3 and the low-speed cam 2.
It must be able to withstand the force generated by the relative difference between the accelerations a and 2b, and in particular, in order to keep the high-speed rocker arm 8 in contact with the high-speed cam 3, the force generated by the acceleration in the negative region must be able to withstand the force generated by the relative difference between the accelerations of (i.e., inertial force).

However, if the spring force is made too strong, it will affect the hydraulic lash adjuster 10 and harm its operation, and the effect of reducing the driving resistance described above will also be weakened. Undesirable.

Therefore, when the biasing spring 20 is arranged as a rains spring in this way, the cam profile of the high-speed cam 3 is intentionally thinned in the region where negative acceleration is generated, so that the low-speed It is better to reduce the relative difference in acceleration between the cams 2a and 2b, and to prevent the output from decreasing in the high rotation range due to this, by extending the lift timing a little.

In addition, when the hydraulic switching means 13 switches the high-speed rocker arm 8 and the low-speed rocker arms 6 and 7 into an interlocked state (ON) or a non-interlocked state (OFF), the hydraulic regulator controls the ON operation. At startup, the high hydraulic pressure generated by the oil pump installed in the engine is directly supplied into the hydraulic chamber 14 to quickly engage the plunger 15 with the low-speed rocker arms 6 and 7, and then the lower limit pressure value for maintaining ON operation is gradually increased. It is desirable to set the pressure so that the pressure is reduced to the vicinity of .

<Effects> In summary, according to this invention, the spring for constantly abutting the high-speed rocker arm against the high-speed cam when the engine is rotating at low speed is spanned between the low-speed rocker arm and the high-speed rocker arm to make it smaller, and is also interposed between the oscillating ends of these arms on the valve side. This makes it possible to lower the overall height of the engine and reduce the amount of energy consumed in expanding and contracting the spring, thereby minimizing the driving resistance of the valve mechanism as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a preferred embodiment of a valve train for an engine according to the present invention, and FIG. 2 is a side sectional view showing the main parts thereof. 1...Camshaft, 2a, 2b...Low speed cam, 3
...High-speed cam, 5...Rotsuka shaft, 6,
7...Locker arm for low speed, 6b, 7b...Arm portion on the valve side, 8...Rotzker arm for high speed, 8b...Arm portion on the valve side, 11...Intake valve, 13...Hydraulic switching means, 20... ...biasing spring.

Claims (1)

[Scope of utility model registration request] Corresponding to the two intake valves provided per cylinder, two valves are installed between each intake valve and the low-speed cam of the camshaft so that they can swing freely on the rocker shaft.
Two low-speed rocker arms are provided, and between these two low-speed rocker arms, there is provided a high-speed rocker arm that is swingably supported on the rocker shaft with one arm abutting the high-speed cam of the camshaft. In an engine valve train, the other arm of the high-speed rocker arm is provided with a hydraulic switching means for switching between the other arm and the low-speed rocker arms on both sides of the high-speed rocker arm in an interlocking state or a non-interlocking state. A valve operating system for an engine, characterized in that a biasing spring is provided that spans between an arm portion and the other arm portion of the high-speed rocker arm to constantly bring the high-speed rocker arm into contact with the high-speed cam. .