JPS63117111A - Device for switching valve operating timing of internal combustion engine - Google Patents

Abstract

PURPOSE:To suitably keep valve clearance of the device in the caption by making it possible to switch connection/disconnection between rocker arms, which are adjacently disposed to each other, and supporting a rocker shaft by means of two hydraulic rash adjustors. CONSTITUTION:Rocker arms 5 through 7 are adjacently disposed to each other on a rocker shaft 8. A piston is slidingly fitted into guide holes, which are internally provided in the rocker arms 5 through 7, so that the displacement of the piston position switches connection/disconnection between the rocker arms 5 through 7. The rocker shaft 8 is supported on a cylinder head 9 through two hydraulic rash adjustors 40. Therefore, valve clearance can be suitably kept.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a switching device that changes the operating timing of an intake valve or an exhaust valve in stages according to the rotational speed of an internal combustion engine.

(Prior Art) The combustion chamber of a four-stroke engine is equipped with an intake valve and an exhaust valve in order to supply the air-fuel mixture to the combustion chamber and discharge combustion gas according to a predetermined cycle. Both of these valves are normally biased in the valve closing direction by a valve spring provided so as to surround the valve stem. Furthermore, both of these valves are forcibly pushed open against the biasing force of the valve spring mentioned above by a cam that is integrally installed on a camshaft that is connected and driven from the engine's crankshaft using a belt, pulley, etc. It is made possible to do so.

On the other hand, multiple intake valves or exhaust valves are provided for each cylinder, and during low-speed operation, one intake valve or exhaust valve is operated, and during high-speed operation, all valves are operated, and at the same time, the operation timing of these valves is adjusted according to the engine rotation. Various techniques have been proposed to improve the filling efficiency of the air-fuel mixture into the combustion chamber over a wide operating range by changing the speed according to the speed.

As such a valve operation timing switching device, for example, in Japanese Unexamined Patent Publication No. 19911-1989 by the present applicant, a camshaft that is rotationally driven in synchronization with the rotation of the engine is used to switch one intake valve or one exhaust valve. A low-speed cam with a shape suitable for low-speed operation of the engine and a high-speed cam with a shape suitable for high-speed engine operation are integrated, and the rocker shaft slides into contact with the low-speed cam, and one intake air A 10th lug arm that can come into contact with a valve or an exhaust valve, a 20th lug arm that comes into contact with the other intake valve or exhaust valve, and a 30th lug arm that comes into sliding contact with a high-speed cam are in sliding contact with each other to allow relative angular displacement. a state in which the first, second and thirtieth lever arms integrally connect the respective rocker arms;
A valve operating body stop device for an internal combustion engine has been proposed which is provided with a connecting means that allows switching between a state that allows relative angular displacement of each rocker arm. As this connecting device, a structure is disclosed in the same specification in which a piston is slid into a guide hole that is formed inside so as to communicate with each other, and the rocker arms can be connected to each other by hydraulically operating this piston. Disclosed.

However, according to the above structure, the guide holes of each rocker arm are aligned with each other in a state where the base circle of the cam is in sliding contact with the cam slipper surface of each rocker arm, and the piston is actuated in this state. Therefore, if the valve clearances (so-called tappet clearances) of adjacent rocker arms are uneven, deviations will occur in the axes of each guide hole, which may impede the smooth sliding movement of the piston. Therefore, in order to maintain an appropriate tappet clearance at all times, maintenance intervals must be shortened, which makes precision maintenance management complicated.

<Problems to be Solved by the Invention> In order to correct such inconveniences, it is basically possible to provide a hydraulic lash adjuster that automatically adjusts the tappet clearance. When trying to install a conventional lash adjuster in a valve train equipped with a switching device, for example, if the lash adjuster is installed at the end of the rocker arm that abuts against the valve stem, the rocker arm must be installed to avoid interference with the switching device. This is undesirable because it becomes large and the inertial mass increases.

A structure in which the rocker arm is pivotably supported by a lash adjuster with a ball joint formed at the tip end of the plunger is also known, which is advantageous in downsizing the rocker arm structure, but it also displaces the rocking center and causes the rocker arm to ball. Since it is supported in a joint type, it is inevitable that the axis of the guide hole of the switching device will be misaligned.

In view of the problems of the prior art, the main object of the present invention is to provide a valve timing switching device for an internal combustion engine in which a hydraulic lash adjuster can be incorporated without impairing the reliability of its operation. It's in particular.

Means for Solving the Problems According to the present invention, such an objective is to provide a low-speed cam that periodically rotates with the crankshaft and is suitable for low-speed operation of the engine, and a high-speed cam that is suitable for high-speed operation of the engine. a camshaft integrally formed with a cam, a valve installed at an intake port or an exhaust port of a combustion chamber and always biased to close by a spring means and driven to open by the cam; Rocker arms corresponding to the high-speed cylindrical cams and pivotally supported on a rocker shaft adjacent to each other so as to impart the lifting height of both of these cams to the valve, and a connecting means for selectively switching between connection and disconnection between these rocker arms. A valve operation timing switching device for an internal combustion engine having: a state in which the connecting means integrally connects both the rocker arms by displacing the position of a piston that is fitted into a guide hole that is inserted in the rocker arms; and a state in which relative positional displacement of each rocker arm is permitted, and the rocker shaft is supported by the engine body via at least two hydraulic lash adjusters. This is achieved by providing a valve operation timing switching device for an internal combustion engine.

<Operation> By doing this, at high speeds, each rocker arm is connected and operated, and the valve is driven to open by a cam suitable for high speed rotation, and at low speeds, the connection between each rocker arm is released, and the cam suitable for low speed rotation is driven. The valve is driven to open.

Since the rocker arms are pivotally supported by the rocker shaft, there is no misalignment between the rocker arms, and the hydraulic lash adjuster maintains appropriate tappet clearance.

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

As shown in FIG. 1, the internal combustion engine main body (not shown) is provided with a pair of intake valves 1a, 1b, and both intake valves 1a, 1b are connected to a crankshaft (not shown).
A pair of low-speed cams 3a, 3b and a single high-speed cam 4 having an oval cross section are provided integrally with a camshaft 2 that is synchronously driven at two speeds, and these cams 3a, 3b, 4 are connected to each other. The opening/closing operation is performed by the action of the first to thirtieth lever arms 5 to 7, which swing together.

The internal combustion engine is also equipped with a pair of exhaust valves (not shown), which are driven to open and close in the same manner as the intake valves 1a and 1b described above.

The first to thirtieth lever arms 5 to 7 are pivotally supported adjacent to each other so as to be swingable on a rocker shaft 8 fixed below the camshaft 2 in parallel with the camshaft 2. The first and thirtieth lever arms 5.7 have basically the same shape, their base ends are pivotally supported by the rocker shaft 8, and their respective free ends 5b, 7b are above the intake valves 1a, 1b. It extends to the upper end of the valve stem of both intake valves.

The 20th claw arm 6 is connected to the first and 30th claw arms 5.
7 and is pivotally supported on a rocker shaft 8. This 20th
The lever arm 6 connects both intake valves from the rocker shaft 8.
. The upper end surface of the lifter 10 that fits into the guide hole 9a formed in the cylinder head 9 is in contact with the guide hole 9a. Moshi Lifter 1
A coil spring 11 is compressed between the inner surface of the guide hole 9a and the bottom surface of the guide hole 9a, and constantly biases the lifter 10 upward.
is in sliding contact with the high-speed cam 4 at all times.

As described above, the camshaft 2 is rotatably supported above the engine body, and the camshaft 2 is rotatably supported above the engine body.
Low-speed cams 3a and 3b corresponding to No. 7 and high-speed cam 4 corresponding to the 20th claw arm 6 are integrally connected. As clearly shown in FIG. 3, the low-speed cams 3a and 3b have a relatively small lift and are formed with a cam profile suitable for low-speed operation of the engine.
, the outer peripheral surface thereof can be slidably contacted with cam slippers 5a, 7a formed on the upper surface of the central portion of the 30th claw arm 5.7. Also, the high speed cam 4 is the low speed cam 3a13.
It is formed with a cam profile suitable for high-speed operation that has a large lifting height over a wider angle than that shown in FIG. . In addition, in Fig. 3, lifter 1
0 is omitted from illustration.

These first to thirtieth lock arms 5 to 7 are connected in one direction by a connecting device 12 to be described later, which is installed in a hole drilled through the center of each rocker arm 5 to 7 and parallel to the rocker shaft 8. It is possible to switch between a state in which it can swing and a state in which it can be relatively displaced.

On the other hand, a retainer 13a is provided at the upper part of both intake valves 1a and 1b.
, 13b are provided respectively, and these retainers 1
Both intake valves 1a, 1b are installed between 3a, 13b and the engine body.
Valve springs 14a and 14b surrounding the stem portion of
is interposed to bias both valves 1a and 1b in the valve-closing direction, that is, upward in FIG. 3.

As shown in FIG. 4, the rocker shaft 8 pivotally supports the rocker arms 5 to 7 adjacent to each other, and has both ends supported by the cylinder head 9 via a pair of hydraulic lash adjusters 40. . A diameter-expanding stepped portion 8a is formed at the left end of the rocker shaft 8 in FIG.
It is in contact with the side end surface of the hook arm 5. A stop ring 16 is fitted to the right end via a thrust washer 1715, and these stop rings 16 for each of the rocker arms 5 to 7.
is prevented from being removed from the rocker shaft 8.

The rocker shaft 8 has mounting holes 1 bored at both ends thereof.
By receiving the hemispherical heads 18a, 18b of the hydraulic lash adjuster 40 in 7a, 17b,
It is combined with the lash adjuster 40. Fan-shaped notches 19a and 19b are formed at the base end portions of the first and thirtieth lock arms 5.7 at the joint between the lash adjuster 40 and the rocker shaft 8 (FIG. 3), and both rocker arms 5. 7 is prevented from being obstructed by the lash adjuster 40.

An oil guide pipe 21 is fixed to the left end of the rocker shaft 8 by a union nut 20, and can supply hydraulic pressure to a coupling device 12, which will be described later, through an oil passage 22 bored in the rocker shaft 8. It is like that.

The hydraulic lash adjuster 40 that supports the rocker shaft 8 is of a known type as shown in FIG. 42 are slid together to define a low-pressure air 43 inside the plunger 42 and a high-pressure chamber 44 between the outer surface of the bottom wall of the plunger 42 and the inner surface of the casing 41.

A through hole 45 is opened in the bottom wall of the plunge t42,
A ball type check valve 46 provided on the high pressure chamber 44 side allows communication of the through hole 45 to be interrupted or interrupted depending on the pressure difference between the two ends 43 and 44. Further, a coil spring 47 is compressed in the high pressure chamber 55, and the plunger 42 is constantly pressed upward. and plunger 4
Oil holes 48 and 49 are formed in the peripheral wall of No. 2 and the peripheral wall of the casing 41, respectively, and lubricating oil is supplied to the inside of the low-pressure air 43 through an oil passage 50 bored in the cylinder head 9.

As clearly shown in FIGS. 6 and 7, a first guide hole 27 that opens toward the 20th claw arm 6 is bored in the 10th claw arm 5 in parallel with the rocker shaft 8. . A reduced diameter portion 28 is formed on the bottom side of the first guide hole 27, and a stepped portion 29 is formed accordingly.

A second guide hole 30 that communicates with the first guide hole 27 of the tenth claw arm 5 is bored through the 20th claw arm 6 between both sides thereof.

A third guide hole 31 communicating with the second guide hole 30 is bored in the 30th claw arm 7 . The bottom side of the third guide hole 31 is formed with a stepped portion 32 and a small diameter portion 33 like the first guide hole 27, and further has a small diameter through hole 34 that penetrates the bottom wall of the third guide hole 31. It is bored concentrically with the third guide hole 31.

Inside these first to third guide holes 27, 30, 31 is a first piston 3 that can move between a position where the first and 20th hook arms 5.6 are connected and a position where the connection is released.
5, a second piston 36 that is movable between a position where the second and 30th hook arms 6.7 are connected and a position where the connection is released, and a stopper 27 that restricts the movement of both pistons 3 and 5.36. A coil spring 38 is installed to bias both pistons 35, 36 toward the disconnection position.

The first piston 35 has a first guide hole 27 and a second guide hole 3.
0 and 1, thereby defining a hydraulic chamber 39 between the bottom surface of the first guide hole 17 and the end surface of the first piston 35. Further, the hydraulic chamber 39 is connected to the oil passage 2 in the rocker shaft 8 via an oil passage 39a bored in the tenth lever arm 5.
2, and the hydraulic oil supplied via the oil guide pipe 21 is supplied to
It is arranged so that it can be introduced into the hydraulic chamber 39 at all times.

The axial dimension of the first piston 35 is such that when one end thereof comes into contact with the stepped portion 29 in the first guide hole 27, the other end does not protrude from the side surface facing the 20th claw arm 6 of the 10th claw arm 5. It is set.

The second piston 36 has an axial dimension equal to the entire length of the second guide hole 30 so that it can slide into the second guide hole 30 and the third guide hole 31.

The stopper 37 has a disk portion 37a formed at one end that fits into the third guide hole 31, and a guide rod 37b inserted into the through hole 34 at the other end. Furthermore, between the disk portion 37a of the stopper 27 and the bottom of the small diameter portion 33 of the third guide hole 31, the coil spring 3 described above surrounds the guide rod 37b.
8 is interposed.

Next, the operation of the apparatus described above will be explained.

Referring to Figure 6.7, in the engine medium and low speed range,
By closing a control valve (not shown), the coupling device 1
Hydraulic pressure is not supplied to the hydraulic chamber 39 of No. 2, and each piston 35
．． 36 is aligned in each guide hole 27, 30 as shown in FIG. 6 by the biasing force of the coil spring 38, so that each rocker arm 5-7 can be angularly displaced relative to each other.

When the coupling device 12 is in the disconnected state, the rotation of the camshaft 2 causes the first and 30th hook arms 5.
7 swings in response to one contact with the low speed cams 3a and 3b,
Both intake valves 1a and 1b are driven to open and close with their closing timings delayed and their closing timings advanced, and their lift amounts reduced. At this time, the 20th lever arm 6 swings due to sliding contact with the high-speed cam 4, but the swinging movement is caused by both intake valves 1a
, 1b have no effect on the operation.

During high-speed operation of the engine, by opening the control valve, the connection device @ 12 is
Hydraulic pressure is supplied to the hydraulic chamber 39 of. As a result, as shown in FIG. 7, the first piston 35 moves toward the 20th lever arm 6 against the biasing force of the coil spring 38, and the second piston 36 is pushed by the first piston 35. and move to the 30th arm 7 side. As a result, stopper 3
The first and second pistons 35 and 36 move together until the disk portion 37a of No. 7 comes into contact with the stepped portion 32, and the first piston 35
The first and 20th lever arms 5.6 are connected, and the second and 30th lever arms 6.7 are connected by the second piston 36.
are concatenated.

As described above, when the first to thirtieth claw arms 5 to 7 are connected to each other by the coupling device 12, the amount of swing of the 20th claw arm 6, which is in contact with the high-speed cam 4, is the largest. Therefore, the first and 30th arm 5
．． 7 swings together with the 20th lug arm 6. Therefore, both intake valves 1a and 1b are driven to open and close together by making their closing timings earlier and later according to the cam profile of the high-speed cam 4, and by increasing their lift amount.

In the valve operation timing switching device configured as described above, if the gap between the links called the so-called tappet clearance is not uniform, the smooth operation of the switching pistons 35 and 36 may be inhibited. Therefore, according to the present invention, the rocker shaft 8
By installing a hydraulic lash adjuster in the tappet clearance, the tappet clearance is automatically adjusted.

As shown in FIG. 3, when the cam slippers 5a, 7a, and 6 are arranged around the base circle C of the cam, no external force acts on the plunger 42 of the lash adjuster 40. Therefore, the plunger 42 is connected to the coil spring 47.
is pushed up only by the urging force of the rocker arm, thereby reducing the gap between the contact surface between the free end of each rocker arm and the valve stem end, and the contact surface between the low-speed cams 3a, 3b and the cam slippers 5a, 7a to O. ing.

When the cams 3a, 3b begin to push the rocker arms 5.7, a force acts in a direction that pushes down both the intake valves 1a, 1b and the plunger 42. As a result, the pressure within the high pressure chamber 44 increases, and the check valve 46 closes the through hole 45. As a result, the hemispherical heads 18a, 18b of both lash adjusters 40
The height position of the intake valves 1a and 1b is fixed, and the intake valves 1a and 1b start to lift while the gap between the contact surfaces is maintained at O.

When the camshaft 2 rotates and the cam slippers 5a and 7a again come into sliding contact with the base circle C portion, the intake valve 1a closes.

1b is closed and the pressure applied to the plunger 42 is reduced, so the check valve 46 opens the through hole 45 and the spring 47
Only the urging force pushes up the rocker shaft 8. The lubricating oil leaking from the oil hole 51 and between the casing 41 and the plunger 42 is replenished through the oil passage 50 formed in the cylinder head 9 and the side holes 48 and 49.

The driving means for the switching piston is not limited to the above-mentioned hydraulic drive, but may also be an electrical or mechanical device.

In the above embodiment, a case has been described in which the operating timing of both valves is switched using a 3-split rocker arm, but the present invention has a configuration in which a 2-split rocker arm is used to stop one valve at a predetermined rotation speed. It is equally applicable to a valve operation timing switching device.

<Effects of the Invention> As described above, according to the present invention, it is possible to incorporate a hydraulic lash adjuster into a valve operation timing switching device very suitably, and it is possible to incorporate a hydraulic lash adjuster into a valve operation timing switching device in a very suitable manner. Since the pulp clearance can always be maintained at an appropriate level, it is effective in increasing the reliability of the operation of the valve operation timing switching device and at the same time promoting maintenance-free operation of the valve mechanism.

[Brief explanation of the drawing]

FIG. 1 is a top view showing a valve train constructed according to the present invention. FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1. FIG. 3 is a partially cutaway view of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. FIG. 5 is an enlarged sectional view showing an example of a hydraulic lash adjuster. FIG. 6 is a sectional view taken along the line Vl--Vl in FIG. 3 during low-speed operation. FIG. 7 is a cross-sectional view similar to FIG. 6 showing the state of high-speed operation. 1a, 1b... Intake valve 2... Camshaft 3a, 3b.
...Low speed cam 4...High speed cam 5...10th lever arm 6
...20th Tsuka Arm 7...30th Tsuka Arm 5a
~7a...Cam slipper 8...Rocker shaft 8a...Expanded diameter stepped portion 9...
Cylinder head 9a...Guide hole 10...Lifter 11...Coil spring 12...Connection device 13a,'13b...Retainer'14a, 14b...Valve spring 15...Thrust washer 16... ...Stop ring 17a, 17b...Mounting hole 18a, "l8b...Head 19a, 19b
... Notch 20 ... Union nut 21 ... Oil guide pipe 22 ... Oil passage 27 ... First guide hole 2
8...Small diameter part 29...Step part 30...Second
Guide hole 31...Third guide hole 32...Step part
33...Small diameter part 34...Through hole 35
...First piston 36...Second piston 37...
・Stopper 37a... Disk portion 37b... Guide rod 37C... Axial groove 38... Coil spring 39
...Hydraulic chamber 39a...Oil passage 40...Hydraulic lash adjuster 41...Casing 42...Plunger 43...
...Low pressure chamber 44...High pressure chamber 45...Through hole
46...Check valve 47...Coil spring
48.49...Oil hole 50...Oil path patent applicant: Honda Motor Co., Ltd. representative
Attorney Patent Attorney Yo Oshima - Figure 1 Figure 2

Claims (1)

[Claims] A camshaft that rotates periodically with the crankshaft and is integrally formed with a low-speed cam adapted to low-speed operation of the engine and a high-speed cam adapted to high-speed operation of the engine; A valve installed in an intake port or an exhaust port, which is normally biased to close by a spring means and driven to open by the cam, and the low-speed and high-speed cams respectively, and the lift height of these cams is set to the valve. A valve operation timing switching device for an internal combustion engine, comprising rocker arms adjacent to each other and pivotally supported on a rocker shaft, and a connection means for selectively switching between connection and non-connection between these rocker arms, the device comprising: The means selectively switches between a state in which both the rocker arms are integrally connected and a state in which relative positional displacement of each rocker arm is allowed by displacing the position of a piston that slides into a guide hole provided in both the rocker arms. A valve timing switching device for an internal combustion engine, characterized in that the rocker shaft is supported by an engine body via at least two hydraulic lash adjusters.