JPS63117110A - Device for switching valve operating timing of internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at improvement in reliability of the switching device in the caption by making it possible to selectively switch connection/disconnection between arm members adjacently disposed to each other, and supporting base end portions of the arm members through hydraulic rash adjustors. CONSTITUTION:Guide boles 26a, 26b are formed in the second rocker arm 6 among rocker arms 5, 6, 7 which are adjacently disposed to each other, and then, pistons 29 are slidingly fitted into the guide holes 26a, 26b, wherein the pistons 29 switch connection/disconnection between the rocker arms 5 through 7. The respective spherical supporting portions 21a, 21b of the rocker arms 5, 7 are supported on a cylinder head 8 through hydraulic rash adjustors. Therefore, tappet clearance can be suitably kept, hence enhancing reliability of a switching device.

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 can abut the other intake valve or exhaust valve, and a 30th lug arm that slides on a high-speed cam slide against each other to enable relative angular displacement. A connecting means is provided which allows the first, second and 30th lock arms to switch between a state in which the rocker arms are integrally connected and a state in which relative angular displacement of the lock arms is allowed each day. A valve operating body stop device for an internal combustion engine has been proposed. As this connecting device, a structure is described in the same specification in which a piston is slid into a guide hole that is arranged 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 operated 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 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 attempting to install a conventional lash adjuster in a valve train equipped with a timing switching device, for example, if the lash adjuster is provided 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 increases the size and inertial mass.

A structure in which the rocker arm is pivoted and supported by a lash adjuster with a ball joint formed at the tip of the plunger is also known, which is advantageous in downsizing the rocker arm structure, but it also displaces the center of swing and causes the rocker arm to pivot. 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. There is a particular thing.

<Means for Solving the Problems> According to the present invention, it is an object of the present invention to provide a low-speed cam that rotates synchronously with the crankshaft and is suitable for low-speed engine operation, and a high-speed cam that is suitable for high-speed engine operation. a camshaft integrally formed with a camshaft, 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; An internal combustion engine comprising arm members corresponding to both cams and arranged adjacent to each other so as to impart the lifting height of both cams to the valve, and a coupling means for selectively switching between coupling and non-coupling between these arm members. In the valve operation timing switching device, the connecting means integrally connects both arm members by selectively displacing the position of a piston that slides into a guide hole provided in both arm members. The arm member can be selectively switched between a state that allows relative positional displacement of each arm member, and the base end of the arm member is swingably supported by the engine body via a hydraulic lash adjuster, Provided is a valve operation timing switching device for an internal combustion engine, characterized in that a free end of the arm member abuts a stem end of the valve and engages with guide means along a sliding axis of the valve. This is achieved by

<Operation> In this way, at high speeds, each arm member is connected and operated, and the valve is driven to open by the cam that is suitable for high speed rotation, and at low speeds, the connection between each arm member is released and it is suitable for low speed rotation. The valve is opened by the cam.

The guide means defines the inclination of the rocker arm along the sliding axis of the valve, and tappet clearance is maintained appropriately without causing any deviation in the axes of the guide holes.

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

1 to 4 show a valve train to which the present invention is applied, and an internal combustion engine main body (not shown) includes a pair of intake valves 1
a, 1b are provided, and these intake valves 1a, 1b
A pair of low-speed cams 3a, 3b and a single high-speed cam, each having an oval cross section, are integrally provided on a camshaft 2 that is synchronously driven at half the speed of a crankshaft (not shown). 4 and
Opening and closing operations are performed by the action of first to thirtieth hook arms 5 to 7, which are arm members that engage with these cams 3a, 3b, and 4 to perform rocking motion. Also,
This internal combustion engine is 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.

As shown in FIG. 2, the first to thirtieth lever arms 5 to 7 have their base ends spherically supported by the cylinder head 8 and are swingable below the camshaft 2. They are pivoted adjacent to each other, and each free end is connected to both cams 3.
It extends above both valves 1a, 1b through below the valves 1a, 3b, 4.

The first and 30th lever arms 5.7 are basically of the same shape, and cam slippers 5a and 7 are provided on the upper surfaces of their intermediate portions so that they can come into sliding contact with the outer peripheral surfaces of the low-speed cams 3a and 3b, respectively.
a is formed, and free ends 5b and 7b abut against the upper ends of the valve stems of both intake valves 1a and 1b, respectively.

The 20th claw arm 6 is connected to the first and 30th claw arms 5.
It is spherically supported by the cylinder head 8 between 7 and 7. This 20th rocker arm 6 is connected to both the first and third rocker arms 5.7.
As shown in FIG. 4, a cam slipper 6a is formed on the upper surface of the intermediate portion to slide into contact with the high-speed cam 4.
A guide hole 8a drilled in the cylinder head 8 is provided on the lower surface.
The upper end surface of the lifter 9 that slides on is in contact with the upper end surface of the lifter 9. A coil spring 10 is compressed between the inner surface of the lifter 9 and the bottom surface of the guide hole 8a, and constantly biases the lifter 9 upward.
However, it is designed so that it can always be in sliding contact with the high-speed cam 4.

Free ends 5b to 7 of these first to 30th hook arms 5 to 7
b are respectively gripped by guide grooves 13 formed in a comb-teeth shape on the free end side of a guide plate 12 fixed to the cylinder head 8 using ports 11. The free end portions 5b to 7b of each rocker arm and the guide groove 13 are in contact with each other with a predetermined tolerance. The rocking axis and the inclination of each rocker arm 5 to 7 are defined.

These first to thirtieth lever arms 5 to 7 are connected by a connecting device 14, which will be described later, which is installed in a hole drilled through the center of each of the lever arms 5 to 7 and parallel to the camshaft 2.
It is possible to switch between a state in which it can swing in one direction and a state in which it can be relatively displaced.

On the other hand, there is a retainer 15a on the upper part of both intake valves 1a and 1b.
, 15b are provided respectively, and these retainers 1
Both intake valves 1a, 1b are installed between 5a, 15b and the engine body.
Valve springs 16a and 16b surrounding the stem portion of
is interposed to bias both valves 1a and 1b in the valve-closing direction, that is, upward in FIG.

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. 1, 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, and the high-speed cam 4 has a relatively small lift. Compared to the low-speed cams 3a and 3b, the cam profile is suitable for high-speed operation and has a large lift over a wider angle.

Ball joint 1 that supports the 20th lug arm 6 on a spherical surface
7 is threadedly connected to the 20th claw arm 6, as best shown in FIG. 4, and has a well-known tappet adjustment function. An oil passage 19 that communicates with a lubricating oil supply passage 18 provided in the cylinder head 8 is bored in the holder 17a screwed onto the cylinder head 8.
At the same time as lubricating oil is guided to the pivot portion of the ball joint 17, driving hydraulic pressure can be supplied to the coupling device 14 through an oil passage 20 bored in the 20th lug arm 6.

A hydraulic lash adjuster 40 having ball joints 21a and 21b formed in its head is provided on the spherical support portion of the first and thirtieth lever arms 5.7.

This hydraulic lash adjuster 40 is of a known type as shown in FIG.
) is formed by sliding the plunger 42 together, a low pressure chamber 43 is formed inside the plunger 42, and the plunger 42
A high pressure chamber 44 is formed between the outer surface of the bottom wall of the casing 41 and the inner surface of the casing 41.
Each of them has been defined.

A through hole 45 is formed in the bottom wall of the plunger 42,
A Pall 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 chambers 43,44. Further, a coil spring 47 is compressed in the high pressure chamber 44, and the plunger 42 is always 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 chamber 43 through an oil passage 50 bored in the cylinder head 8. The ball joint 21a (21b) is lubricated through the oil hole 51 in the head of the plunger 42.

As clearly shown in FIGS. 2 and 3, the 1st and 30th
The lever arm 5.7 has a second
First and fourth guide holes 22a and 22b, which are open toward the zero tension arm 6 side, are formed parallel to the camshaft 2, respectively. At the bottom sides of both guide holes 22a, 22b, reduced diameter portions 23a, 23b are formed, respectively, and step portions 24a, 24b are formed accordingly. Further, small diameter through holes 25a, 25b penetrating the bottom walls of both the guide holes 22a, 22b are provided.
They are each drilled concentrically with 2b.

The 20th hook arm 6 has second and third guide holes 26a and 26b that communicate with the first and fourth guide holes 22a and 22b on both sides, which are line-symmetrical from the center, and these guide holes 26a and 26b are connected to each other. A communicating small diameter portion 27 is formed, and step portions 28a and 28b are formed accordingly. The central small diameter portion 27 is connected to the holder portion 17a through an oil passage 20 bored in the 20th lug arm 6.
The small diameter portion 27 is connected to the oil passage 19 of the small diameter portion 27, so that hydraulic pressure can be introduced into the small diameter portion 27.

Inside the second and third guide holes 26a and 26b, there are
A pair of pistons 29 that can move between a position where the 30th hook arms 5 to 6 are connected and a position where the connection is released are slidably connected to each other, and the first and fourth guide holes 22a and 22b
Inside, there is a pair of stoppers 30 that define the moving distance of both pistons 29, and together with the stoppers 30, both pistons 29 are moved.
A pair of coil springs 31 are attached to each of the coil springs 31 for biasing the coil springs 9 toward the disconnection position.

The axial dimension of both pistons 29 received in the 20th lever arm 6 is such that one end thereof is connected to the second and third guide holes 26a and 26a.
6b, when the other end contacts the first and 30th claw arms 5.7 of the 20th claw arm 6,
It is set so that it does not protrude from the side facing the room.

The stopper 30 has both first and fourth guide holes 22a at one end,
A disc portion 30a is formed to slide on 22b, and a guide rod 30b is formed at the other end to be inserted into through holes 25a and 25b. Further, between the disk portion 30a of the stopper 3o and the bottoms of the small diameter portions 23a, 23b of the first and fourth guide holes 22a, 22b, the aforementioned coil springs 31 are wound around the guide rod 30b. equipped.

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

Referring to Figure 2.3, for the medium and low speed range of the engine,
By closing a control valve (not shown), the coupling device 1
Hydraulic pressure is not supplied to the small diameter portion 27 at the center of each piston 29, and each piston 29 is aligned in the second and third guide holes 26a and 26b as shown in FIG. 2 by the biasing force of each coil spring 31. Each rocker arm 5-7 is therefore capable of relative angular displacement with respect to each other.

When the coupling device 14 is in the disconnected state, the rotation of the camshaft 2 causes the first and 30th hook arms 5.
7 swings in response to sliding contact with the low-speed cams 3a and 3b, and both intake valves 1a and 1b are driven to open and close by delaying their closing timing and advancing their closing timing, and also by reducing the amount of lift. be done. 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 1a1
It has no effect on the operation of 1b.

During high-speed operation of the engine, by opening the control valve, the small diameter at the center of the coupling device 14 is The hydraulic pressure is supplied to the section 27 . As a result, as shown in FIG. 3, both pistons are
Each moves outward against the urging force of both coil springs 31.

As a result, the disc portion 30a of both stoppers 30 is moved to the stepped portion 24a.
, 24b, both pistons 29 move together,
1st and 20th lever arms 5.6 by one piston
are connected, and the second and thirtieth claw arms 6.7 are connected by the other piston.

As described above, when the first to 30th lever arms 5 to 7 are connected to each other by the coupling device 14, the amount of swing of the 20th lever arm 6 in sliding contact with the high-speed cam 4 is the largest. Therefore, the first and 30th lever arms 5.
7 swings together with the 20th lug arm 6. Therefore, both intake valves 1a and 1b are driven to open and close together, with their closing timings being earlier and later according to the cam profile of the high-speed cam 4, and the lift amount being increased.

In the valve operation timing switching device configured as described above, if the gap between the links called tappet clearance is not uniform, the smooth operation of the piston 29 of the coupling device 14 may be inhibited. Therefore, according to the present invention, the tappet clearance is automatically adjusted by providing a hydraulic lash adjuster in the link.

As shown in FIG. 1, when each cam slipper 5a to 7a is in sliding contact with the base circle C of each cam, no external force acts on the plunger 42 of the lash adjuster 40, and therefore, The plunger 42 is pushed up only by the biasing force of the coil spring 47, and this causes the contact surfaces between the free ends 5b, 7b of the double-ended hook arm 5.7 and the valve stem end, the low speed cams 3a, 3b, and the cam slipper 5a to ,7a
The gap between the abutting surfaces is set to O.

When the cams 3a, 3b begin to push the double-ended hook arm 5.7, a force acts in a direction that pushes down both the intake valves 1a, 1b and the plunger 42. Therefore, the pressure within the high pressure chamber 44 increases, and the check valve 46 closes the passage hole 45. As a result, the ball joints 21a, 2 of the plunger head
The height position of 1b is fixed, and both intake valves 1a and 1b start to lift while the gaps between their respective contact surfaces are maintained at O.

The camshaft 2 rotates, and the cam slippers 5a and 7a are placed on the base circle C again! When the two intake valves 1a and 1b close, the pressure applied to the plunger 42 decreases.
Check valve 46 opens through hole 45, and only the biasing force of spring 47 pushes up the proximal end of double-ended hook arm 5.7. Lubricating oil leaking from the oil hole 51 and between the casing 41 and the plunger 42 is replenished through the oil passage 50 and both 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 addition, in the above embodiment, the 3-part rocker arm has 2 parts.
Although the description has been given of a system in which the operating timing of both valves is switched, the present invention is equally applicable to a valve operating timing switching device configured to stop one valve at a predetermined rotational speed using a two-part rocker arm. .

<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 tappet clearance can always be maintained at an appropriate level, it is effective in increasing the reliability of the operation of the valve timing switching device and at the same time promoting maintenance-free valve train mechanisms.

[Brief explanation of the drawing]

FIG. 1 is a partially cut-away view of a valve train constructed according to the present invention as seen from the arrow in FIG. FIG. 2 is a partially cutaway view taken along arrows 1--2 in FIG. 1, showing the state of low-speed operation. FIG. 3 is a cross-sectional view of a main part taken along the line ■--■ in FIG. 1 during high-speed operation. FIG. 4 is a sectional view taken along the line IV--IV in FIG. 2. FIG. 5 is an enlarged sectional view showing an example of a hydraulic lash adjuster. 1a, 1b... Intake valve 2... Camshaft 3a, 3b.
...Low speed cam 4-...High speed cam 5...10th hook arm 6
...20th Tsuka Arm 7...30th Tsuka Arm 5a
~7a...Cam slipper 5b~7b...Free end portion 8...Cylinder head 8a
... Guide hole 9 ... Lifter 10 ... Coil spring 11 ... Bolt 12 ... Guide plate 1
3... Guide groove 14... Connection device 15a, 15b... Retainer 16a, '16b... Valve spring 17... Ball joint 17a... Holder 18... Lubricating oil supply passage 1
9.20...Oil passages 21a, 21b...Ball joint 22a...First guide hole 22b...Fourth guide hole 23a, 23b-
...Small diameter portions 24a, 24b...Stepped portions 25a, 25b...
Through hole 26a...Second guide hole 26b...Third guide hole 27...Small diameter part 28a, 28b...Step part 29...Piston 30...Stopper 30a
...Disc part 30b...Guide rod 31...Coil spring

Claims (1)

[Claims] A camshaft that rotates synchronously with the crankshaft and is integrally formed with a low-speed cam that 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 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 arm members disposed adjacent to each other to provide the same timing, and a connecting means for selectively switching between coupling and non-coupling between these arm members, the coupling means comprising: Selection between a state in which both arm members are integrally connected by selectively displacing the position of a piston that slides into a guide hole provided in both arm members, and a state in which relative positional displacement of each arm member is allowed. Switching is possible, and the base end of the arm member is swingably supported by the engine body via a hydraulic lash adjuster, and the free end of the arm member is connected to the stem end of the valve. Along with coming into contact with
A valve operation timing switching device for an internal combustion engine, characterized in that the device engages with guide means along the sliding axis of the valve.