JPH055206Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] <Field of industrial application> The present invention relates to an improvement of a switching device that changes the operating state of an intake valve or an exhaust valve in stages according to the rotational speed of an internal combustion engine. .

<Prior art> In order to supply the air-fuel mixture to the combustion chamber and discharge the combustion gas at predetermined timings,
A combustion chamber of a four-stroke internal combustion engine includes an intake valve and an exhaust valve, and both of these valves are normally biased in the closing direction by a valve spring provided so as to surround a 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, in order to improve the filling efficiency of air-fuel mixture into the combustion chamber over a wide range of rotational speeds, various techniques have been proposed for changing the operating state of a valve in accordance with the rotational speed of the engine.

As such a valve operation state switching device, for example, in Japanese Patent Application Laid-open No. 16111/1983 by the present applicant,
A pair of low-speed cams each corresponding to a pair of intake valves or exhaust valves and having a shape corresponding to the low-speed rotation range of the engine, and a single high-speed cam having a shape corresponding to the high-speed rotation range of the engine are connected to the engine. Through a pair of direct-acting rocker arms and idle biasing means, which are integrally arranged adjacent to a camshaft that is rotationally driven in synchronization with the rotation, and which directly engage the intake valve or exhaust valve and slide into low-speed cam. The floating rocker arm that slides on the high-speed cam is arranged adjacent to the rocker shaft so that it can be relatively angularly displaced, and these rocker arms are integrally connected, and the linearly moving and floating rocker arms are allowed to have relative angular displacement between them. A valve operating state switching device for an internal combustion engine has been proposed in which each rocker arm is provided with a connecting means that enables switching of the valve operating state. As this connection means, a piston is slid into a guide hole provided internally so as to communicate between each rocker arm, and this piston is hydraulically driven to straddle between adjacent rocker arms, thereby connecting each rocker arm. A structure is disclosed in the same specification that allows the linking of .

According to the above structure, each guide hole is coaxially aligned when the cam slipper of each rocker arm is in sliding contact with the base circle of the corresponding cam. Therefore, at this time, if the piston is moved to a position where it straddles the adjacent rocker arms, both rocker arms are connected to each other.

<Problems to be solved by the invention> On the other hand, if the rocker arms are in a state of relative displacement to each other and the opening of the guide hole is completely exposed from the contour of the adjacent rocker arm, the piston may fall out of the guide hole. There is a risk that it will happen. Additionally, there is some gap between the opposing surfaces of the rocker arms that are adjacent to each other, but if the overlap between the tip surfaces of adjacent pistons disappears, the tips of the pistons that protrude into this gap will interfere with each other. It is possible that

In order to prevent this, the piston must be installed at a position where the amount of relative displacement is relatively small, or the piston diameter must be set such that an overlap margin can be ensured.

However, in order to reduce the inertial weight of the valve mechanism, there is a desire to make the rocker arm as thin as possible, and being subject to the above restrictions is not desirable in terms of the design of the valve mechanism.

The present invention was devised in view of the disadvantages of the prior art, and its main purpose is to provide a valve train equipped with a cam follower coupling device having a sliding member such as a piston that slides into a guide hole. An object of the present invention is to provide a valve operating state switching device for an internal combustion engine that is improved in order to reduce design constraints regarding a coupling device.

[Structure of the invention] <Means for solving the problem> According to the invention, this purpose is to provide a valve that is installed at the intake port or exhaust port of the combustion chamber and is normally biased to close by a spring means. at least two cam followers disposed adjacent to each other so as to be relatively displaceable in a direction orthogonal to the sliding surface or the opposing surface in order to transmit the lift of the cam rotating in synchronization with the crankshaft; A guide hole of the same diameter is formed in each of the cam followers so as to be coaxial and alignable in a direction perpendicular to the sliding surface or the opposing surface, and the guide hole can be selectively inserted from one side of the guide hole toward the other. A valve operating state switching device for an internal combustion engine having a sliding member,
By providing a valve operation state switching device for an internal combustion engine, wherein the sliding surface or opposing surface of the cam follower has a guide surface that can overlap the tip surface of the sliding member over the entire relative displacement range. achieved. In particular, it is preferable to form a chamfer on the tip end surface of the sliding member.

<Operation> In this way, the distal end surface of the sliding member comes into contact with the guide surface, and it is possible to prevent the sliding member from falling off from the guide hole. In addition, if there is no overlap between the tip surfaces of the sliding members, the chamfers formed on the opposing ends will cause the tip surfaces of the sliding members to slide into contact with each other and push each other apart. Does not inhibit exercise.

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

As shown in FIG. 1, a pair of intake valves 1a and 1b are provided in the internal combustion engine body (not shown). Both intake valves 1a and 1b are provided with a low-speed cam 3 and a high-speed cam, each having a predetermined profile, which are integrally provided on a camshaft 2 that is synchronously driven at half the speed of a crankshaft (not shown). 4, and first to third rocker arms 5 as cam followers that engage with the cams 3 and 4 to perform rocking motion.
-7 are used to perform opening and closing operations. 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.

Each of the rocker arms 5 to 7 is pivotally supported adjacent to each other so as to be swingable on a rocker shaft 8 that is fixed below the camshaft 2 in parallel to the camshaft 2. Of these, the first and second rocker arms 5,
The valves 7 have basically the same shape, their bases are pivotally supported by the rocker shafts 8, and their free ends extend above each intake valve 1a, 1b. Moreover, tappet screws 9a, 9b which abut the upper ends of the respective intake valves 1a, 1b are screwed into the free ends of both rocker arms 5, 7 so as to be movable forward and backward.
are each prevented from loosening by lock nuts 10a and 10b.

The third rocker arm 6 is pivotally supported on the rocker shaft 8 between the first and second rocker arms 5 and 7. This third rocker arm 6 extends slightly from the rocker shaft 8 toward the middle of both intake valves 1a, 1b, and as shown in FIG. is formed on the upper surface of the free end, and the cylinder head 11
The upper end surface of the lifter 12, which serves as a floating biasing means and slides into a guide hole 11a formed in the guide hole 11a, is in contact with the lower surface of the lifter 12.

The lifter 12 has a cylindrical shape with a bottom, and a coil 13 is compressed inside thereof. As a result, the third rocker arm 6 is
a is elastically biased so that it is always in sliding contact with the high-speed cam 4.

As described above, the camshaft 2 is rotatably supported above the engine body, and includes a low speed cam 3 corresponding to the first rocker arm 5 and a high speed cam 4 corresponding to the third rocker arm 6. A raised portion 2a having a perfect circular contour equal to the base circle of the two cams 3 and 4 corresponding to the second rocker arm 7 is adjacent to and integrally connected to each other. As clearly shown in FIG. 3, the low-speed cam 3 is formed in a cam profile suitable for the low-speed rotation range of an engine having a relatively small lift, and is formed on the upper surface of the first rocker arm 5. The outer peripheral surface of the cam slipper 5a can be brought into sliding contact with the cam slipper 5a. Furthermore, the high-speed cam 4 is formed with a cam profile that is suitable for the high-speed rotation range of the engine, which has a larger lift over a wider angle than the low-speed cam 3, and as described above, the cam slipper of the third rocker arm 6 is Its outer peripheral surface is in sliding contact with 6a. The raised portion 2a is in sliding contact with a cam slipper 7a formed on the upper surface of the second rocker arm 7, and the raised portion 2a is in sliding contact with a cam slipper 7a formed on the upper surface of the second rocker arm 7.
The vibration of the rocker arm 7 is suppressed. Note that the lifter 12 is not shown in FIG. 3.

Each of these rocker arms 5 to 7 is in a state where it can swing integrally by a connecting device 14, which will 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. and a state in which relative displacement is possible.

On the other hand, retainers 15a and 15b are provided above each intake valve 1a and 1b, respectively. At the same time, valve springs 16a and 16b are interposed between the retainers 15a and 15b and the engine body, respectively, and surround the stems of the intake valves 1a and 1b.
a and 1b are always elastically biased in the valve closing direction, that is, upward in FIG.

As clearly shown in FIGS. 4 and 5, a first guide hole 17 that opens toward the third rocker arm 6 side is bored in the first rocker arm 5 in parallel with the rocker shaft 8. As shown in FIGS. This first guide hole 17
A reduced diameter portion 18 is formed on the bottom side, and a stepped portion 19 is formed accordingly.

The third locking arm 6 has the first locking arm 5.
A second guide hole 2 that can communicate with the first guide hole 17 of
0 is drilled through between both sides thereof.

A third guide hole 21 that can communicate with the second guide hole 20 is bored in the second rocker arm 7 .
The bottom side of the third guide hole 21 is formed with a small diameter portion 22 and a stepped portion 23, similar to the first guide hole 17, and furthermore, a through hole 24 is bored in the bottom wall of the third guide hole 21. Inside the first to third guide holes 17, 20, 21, there is a first piston 25 that can move between a position where the first rocker arm 5 and the third rocker arm 6 are connected and a position where the connection is released. 3. A second piston 26 that is movable between a position where the rocker arm 6 and the second rocker arm 7 are connected and a position where the connection is released, a stopper 27 that defines the moving distance of both pistons 25 and 26, and both pistons 2.
5, 26 and a coil spring 28 that always biases the stopper 27 toward the disconnection position.

The first piston 25 is connected to the first guide hole 17 and the second
It slides into the guide hole 20, thereby defining a hydraulic chamber 29 between the bottom surface of the first guide hole 17 and the end surface of the first piston 25. This first piston 2
The axial dimension of 5 is such that one end thereof is connected to the first guide hole 1.
When it comes into contact with the stepped portion 19 in 7, the other end
It is set so as not to come into contact with the side surface of the rocker arm 6.

The second piston 26 has a second axial dimension.
The length is approximately equal to the entire length of the guide hole 20 and can be slidably fitted into the second guide hole 20 and the third guide hole 21 .

The stopper 27 has a disk portion 27a formed at one end thereof that slides into the third guide hole 21, and has a disk portion 27a that slides into the third guide hole 21
A guide rod 27b that is inserted into the other end is formed at the other end. Further, between the disk portion 27a of the stopper 27 and the bottom of the small diameter portion 22 of the third guide hole 21, the above-mentioned coil spring 28 is contracted so as to surround the guide rod 27b.

A hydraulic oil supply passage 30 is bored in the rocker shaft 8 and communicates with a hydraulic pressure supply device (not shown). The hydraulic oil is supplied from the hydraulic oil supply passage 30 through an oil passage 31 bored to communicate with the hydraulic chamber 29 of the first rocker arm 5, regardless of the swinging state of the first rocker arm 5. can be introduced into the hydraulic chamber 29 as necessary. In addition, the coil spring 28 described above
is bent when the hydraulic pressure acting on the hydraulic chamber 29 reaches a predetermined value or more.

Next, the operating procedure of the apparatus described above will be explained.

In the middle and low speed range of the engine, the supply of hydraulic pressure to the hydraulic oil supply passage 30 is cut off by closing a control valve (not separately shown). Then,
Due to the urging force of the coil spring 28, each piston 25, 26 is aligned in each guide hole 17, 20, respectively, as shown in FIG.
~7 are capable of relative angular displacement with respect to each other.

When the coupling device 14 is in the disconnected state, the first rocker arm 5 swings in response to sliding contact with the low-speed cam 3 due to the rotational movement of the camshaft 2.
One intake valve 1a corresponding to this is driven to open and close by retarding its opening timing and advancing its closing timing, and also by reducing its lift amount.

On the other hand, the second rocker arm 7 does not swing because the raised portion 2a is perfectly circular, so the other intake valve 1b remains closed. Also, at this time, the third rocker arm 6 swings due to sliding contact with the high-speed cam 4, but the swinging action is similar to that of both the intake valves 1a and 1.
It has no effect on the operation of b.

During high-speed operation of the engine, hydraulic pressure is supplied to the hydraulic chamber 29 of the coupling device 14 via the hydraulic oil supply passage 30 and the oil passage 31 of the rocker shaft 8 by opening the control valve. As a result, as shown in FIG. 4, the first piston 25 moves toward the third rocker arm 6 against the pressing force of the coil spring 28, and the second piston 26 is pushed by the first piston 25 and moves toward the third rocker arm 6. 2 Move to the rock arm 7 side. As a result, the first and second pistons 25 and 26 move together until one end of the stopper 27 comes into contact with the stepped portion 19, and the first piston 25 causes the first rocker arm 5 to move.
and the third rocker arm 6 are connected, and the third rocker arm 6 and the second rocker arm 7 are connected by the second piston 26.

As described above, when the rocker arms 5 to 7 are connected to each other by the connecting device 14, the third rocker arm 6 in sliding contact with the high-speed cam 4
Since the amount of rocking becomes the largest, the first and second rocker arms 5 and 7 rock together with the third rocker arm 6. Therefore, both the intake valves 1a and 1b are driven to open and close together by making the opening timing earlier and the closing timing later according to the cam profile of the high-speed cam 4, and also by increasing the lift amount.

Now, in the low speed rotation range where each rocker arm 5 to 7 is in an independent state, the relative displacement angle between the second and third rocker arms 6 and 7 is the largest,
It can be seen that with the position of the coupling device 14 or the amount of valve lift shown in FIG. 3, there is no overlap between the opposing end surfaces of the second piston 25 and the stopper 27.

On the other hand, both the first and second pistons 25, 2 on the first rocker arm 5 and third rocker arm 6 side in FIG.
As seen in the relationship of 6, both rotsuka arms 5,
If the end surfaces of both pistons 25 and 26 overlap each other when the pistons 6 are relatively displaced, smooth relative rocking motion can be performed without mutual interference between the pistons or between the rocker arm and the piston.

However, as in the relationship between the second piston 26 and the stopper 27, if the opposite ends of the two pistons are completely different from each other, the ends of the second piston 26 and the stopper 27 or the side surface of the rocker arm and the end of the piston may This has the disadvantage of causing mutual interference.

Therefore, in the present invention, as shown in FIG. 6, the second piston 26 or the stopper 2
A smooth guide surface 32 corresponding to the relative swing angle range is provided on the side surface of the rocker arm opposite to the tip surface of 7.
a, 32b are partially formed. This prevents the second piston 26 or the stopper 27 from falling out of the guide holes 20, 21.

At the same time, the second piston 26 and stopper 27
Chamfers 33a and 33b each having a partially arcuate curved surface are formed on the mutually opposing tips of the two. As a result, even if the end of the second piston 26 or the stopper 27 protrudes from the side surface of each rocker arm 6, 7, the chamfered portions 33a, 33
The ends of each other slide into contact with each other with b, and the second piston 2
6 and the stopper 27 can be pushed away from each other easily.

A slight gap (dimension g in Fig. 6) is provided between adjacent rocker arms to reduce frictional resistance, and this gap is formed by chamfering 32a, 32b of the second piston 26 and stopper 27. Needless to say, the dimensions are such that it can be easily climbed over with a curvature of .

[Configuration of the invention] As described above, according to the invention, smooth relative movement of the cam followers such as rocker arms can be performed without creating an overlap between the opposing pistons, so that the piston position, piston diameter, valve lift amount, etc. The degree of freedom in designing a valve train having this type of operating state switching device can be expanded. Furthermore, even if some of the cam followers move freely in a low-speed rotation range and the deflection angle becomes excessive due to inertia force, the piston position can be maintained, so it is effective as a fail-safe mechanism.

[Brief explanation of the drawing]

FIG. 1 is a top view of a valve train having a valve operation state switching device constructed based on the present invention. Second
The figure is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a view taken in the direction of the arrows in FIG. 1. FIG. 4 is a sectional view taken along the - line in FIG. 3 during low speed operation. FIG. 5 is a cross-sectional view similar to FIG. 4 showing the state of high-speed operation. FIG. 6 is an enlarged cross-sectional view of a portion of FIG. 5 for explaining the relationship between each part. 1a, 1b...Intake valve, 2...Camshaft, 2a...
...Protuberance, 3...Low speed cam, 4...High speed cam, 5...First rocker arm, 6...Third rocker arm, 7...Second rocker arm, 5a, 6a,
7a...Kamsuritsupa, 8...Lotsukashaft,
9a, 9b... Tappet screw, 10a, 10b...
... Lock nut, 11 ... Cylinder head, 11
a...Guide hole, 12...Lifter, 13...Coil spring, 14...Connection device, 15a, 15b...
Retainer, 16a, 16b... Valve spring, 17... First guide hole, 18... Small diameter portion, 1
9...Step part, 20...Second guide hole, 21...Third guide hole, 22...Small diameter part, 23...Step part, 2
4...Through hole, 25...First piston, 26...
2nd piston, 27...Stopper, 28...Coil spring, 29...Hydraulic chamber, 30...Hydraulic oil supply passage, 31...Oil passage, 32a, 32b...Guide surface, 33a, 33b...Partial spherical surface Chamfered part.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In order to transmit the lift of a cam that rotates in synchronization with the crankshaft to a valve that is installed at the intake port or exhaust port of the combustion chamber and is normally biased to close by a spring means, at least two cam followers arranged adjacent to each other so as to be relatively displaceable in a direction perpendicular to the sliding surface or the opposing surface, and each of the two cam followers in a direction perpendicular to the sliding surface or the opposing surface. A valve operating state switching device for an internal combustion engine, comprising guide holes of the same diameter that are coaxially and alignably bored, and a sliding member that can be selectively inserted from one side of the guide holes to the other. A valve operating state switching device for an internal combustion engine, characterized in that the sliding surface or opposing surface of the cam follower has a guide surface that can overlap the tip end surface of the sliding member over the entire relative displacement range. (2) The valve operating state switching device for an internal combustion engine according to claim 1, wherein a tip end surface of the sliding member has a chamfered portion.