JPH0610099Y2 - Locker arm support device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a rocker arm supporting device for rockably supporting a rocker arm for transmitting a displacement of a cam to a valve at a top portion of an engine. is there.

[Prior Art] Generally, in an overhead valve engine, a rocker arm provided above a cylinder head transmits the vertical displacement of a push rod in contact with a cam to a valve to open and close the valve. As an example of the arm,
For example, a boat-shaped rocker arm described in JP-A-59-166757 is known. The boat-shaped rocker arm is
It is swingably supported by a supporting member provided upright on the cylinder head, and is characterized in that a rocker arm shaft is not used.

Further, conventionally, when the engine is cold, a gap (hereinafter referred to as tappet clearance) is provided between the rocker arm and the valve stem, and when the engine warms up, the valve stem cannot be normally opened and closed due to thermal expansion of the valve stem. I try to prevent it.

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, the boat rocker arm is often manufactured by sheet metal press molding, and in a low-cost general-purpose engine, the push rod contacting the cam is made of iron, Aluminum cylinder and cylinder head
It is often manufactured by die casting. Therefore, when the engine is cold, the tappet clearance is set to, for example, 0.
Even when set to 1 to 0.15 mm, the iron push rod can be relatively moved due to the difference in the linear expansion coefficient between the iron push rod, the aluminum die cast cylinder, and the cylinder head when the engine is warmed up. By shortening the tappet clearance, for example, 0.5 to
Increase to 1.0 mm. That is, the gap between the other end of the rocker arm and the upper end of the valve stem becomes large.

On the other hand, the upper end of the push rod is in contact with one end of the rocker arm, and the lower end of the push rod is in sliding contact with the sliding surface of the cam.

When the cam is rotated in such a state, the push rod reciprocates in the axial direction with the lift amount shown by the solid line L1 in FIG. 3, and pushes up one end of the rocker arm in the forward stroke thereof. Oscillating around the fulcrum of the central portion thereof, and after the predetermined ramp portion (running portion) R1 on the sliding surface of the cam has passed, the other end portion of the arm pushes down the upper end portion of the valve stem. Open the valve.

[Problems to be solved by the device]

However, as described above, when the gap between the rocker arm and the valve stem becomes large, the length of the ramp portion until the other end of the arm abuts the upper end portion of the valve stem to start opening the valve. , R1 to R2, for example.

When the other end of the arm comes into contact with the upper end of the valve stem after such a long ramp portion, the lift amount indicated by the solid line L1 with respect to the cam rotation angle at the time of contact is steep. The other end of the arm comes into contact with the upper end of the valve stem with a strong impact force, and a strong tapping sound (tapping sound) is generated at the time of the contact.

Therefore, this strong tapping sound propagates into the passenger compartment and gives an occupant a discomfort.

When the other end of the rocker arm contacts the upper end of the valve stem, the lower surfaces of both ends of the rod contact the push rod and the valve stem, and
The upper surface of the central portion abuts on the head portion of a rod-shaped rocker arm support member fixed to the top portion of the engine.

In such a contact state, when the other end of the rocker arm applies a strong impact force to the upper end of the valve stem as described above, its reaction force causes the center part of the rocker arm to move. Strong bending stress acts on the fulcrum and pushes up both ends in a V-shape. As a result, the rocker arm may be deformed.

In order to improve this, it is considered that the lift amount of the cam with respect to the cam rotation angle is made gentle as shown by an imaginary line L2 to smooth the rocking of the rocker arm and weaken the impact force applied to the rocker arm. However, if this is done, the cam lift amount L fluctuates,
As the cam lift amount itself is indicated by the broken line L2,
It becomes less, and the timing of opening and closing the valve becomes abnormal.
Moreover, the valve opening time area A on the broken line L2 is reduced, and the engine performance may be deteriorated.

Furthermore, with the ramp portion R2 of the cam kept long, the solid line L1
If an attempt is made to obtain the same lift amount L as above, the diameter of the base circle of the cam becomes abnormally large, which necessitates a large distance between the crankshaft and the camshaft, leading to an increase in size of the engine.

This also has substantially the same problem in the rocker arm rocking prevention device for an overhead valve engine disclosed in Japanese Utility Model Laid-Open No. Sho 60-092708.

Further, in the related art, in U.S. Pat.No. 3,964,455, a substantially boat-shaped rocker arm is supported by a rod-shaped support member fixed to the top of the engine so that its central portion is swingable and axially movable. A compression spring is fitted to the support member, and the lower end of the spring is brought into contact with the upper surface of the central portion of the arm via a pivot member, and the upper end of the spring is brought into contact with a nut fixed to the distal end portion of the support member. Further, there is disclosed a valve control mechanism in which the lower surface of the central portion of the rocker arm is swingably supported by a vertically movable piston via a spacer.

In the above structure, the piston is held in the lowered position by being biased by the spring force of the spring, and in this lowered position, the center portion of the rocker arm is held between the spacer and the pivot member from the upper and lower surfaces thereof and rocks. It is movably supported.

When the cam is rotated in this state, the push rod reciprocates in the axial direction with the lift amount shown by the solid line L1 in FIG. One end of the spacer is pushed up, and the spacer and the pivot member pivotally move about a central portion whose upper and lower surfaces are held as a fulcrum.

By this swinging motion, the other end of the arm pushes down the upper end of the valve stem to open the valve.

However, according to the above configuration, the central portion of the rocker arm is sandwiched between the spacer and the pivot member, and is constrained to the lower position of the piston, and is regulated and held at a predetermined position. When the gap between the rocker arm and the valve stem becomes large due to the difference in thermal expansion between the constituent members, the other end of the rocker arm is located at the upper end portion of the valve stem, almost in the same manner as described in detail in JP-A-59-166757. On the other hand, they may come into contact with each other with a strong impact force, which may cause a strong hammering sound or deformation of the rocker arm.

Next, when the piston is held in the raised position against the spring force of the spring, in the raised position, the central portion of the rocker arm is swingably supported while being held between the spacer and the pivot member. To be done.

However, in this state, even if the cam is rotated, since the push rod is sufficiently separated from the one end of the rocker arm, the arm cannot be oscillated. Therefore, since the opening / closing operation of the valve is not performed,
This engine is kept inactive. That is, this valve control mechanism can achieve the operation and non-operation of the engine by the vertical movement of the piston.

By the way, in the non-operating state of the engine, one end of the rocker arm is sufficiently separated from the push rod, so that the arm may perform an unstable swinging motion.

Therefore, a push rod plunger is axially movably fitted to the tip of the push rod, and the plunger is pushed up by a compression spring housed in the push rod to abut one end of the rocker arm. This prevents the arm from making an unstable swinging motion.

That is, according to the above configuration, in order to achieve the inoperative state of the engine, it is necessary to equip the tip end portion of the push rod with the push rod plunger and the compression spring, and not only the structure thereof is extremely complicated, A strong hammering sound is generated when the engine is operating, and the rocker arm may be deformed.

In the above structure, the center portion of the rocker arm is not sandwiched between the spacer and the pivot member, that is,
It is possible to adopt a structure in which the spacer and the piston are omitted.

However, with such a structure, when the cam is rotated and the push rod is reciprocated in the axial direction with the lift amount shown by the solid line L1 in FIG. 3, the fulcrum of the rocker arm is displaced by the compression spring. Due to the fluctuation, the lift amount of the cam (solid line L1) and the push-down amount that pushes down the upper end portion of the valve stem at the other end portion of the arm do not relatively match, and the valve opening / closing timing is abnormal. And the engine performance is reduced.

The present invention has been made to solve the above problems, and provides a rocker arm support device that has no engine noise and deformation of the rocker arm, has a simple structure, and has good engine performance. To aim.

[Means for Solving the Problems]

A rocker arm support device according to the present invention supports a rocker arm support member fixed to the top of an engine so as to swingably and axially move the center part of a rocker arm having a substantially boat shape, and a cylindrical pivot member. Is fitted to the support member so as to be axially movable and brought into contact with the upper surface of the central portion of the rocker arm, and an adjusting member for restricting the axial movement position of the pivot member is fixed to the tip end portion of the support member, and a buffer spring. Both ends of the elastic body made of are brought into pressure contact with the pivot member and the adjusting member.

[Action]

In the above structure, the rocker arm has a central portion supported by the elastic body via the pivot member so as to be displaceable in the axial direction of the support member, and the tappet clearance is zero.

When the cam is rotated in this state, the push rod reciprocates in the axial direction with a predetermined lift amount, and one end of the rocker arm is pushed up in the forward stroke.

In the process of pushing up, the arm uses the other end as a fulcrum, pushes up the pivot member against the spring force of the buffer spring, and brings the upper end of the pivot member into contact with the adjusting member.

After this contact, the arm swings around the lower end surface of the pivot member as a fulcrum, and the other end pushes down the upper end of the valve stem to open the valve.

That is, the upper end of the pivot member receives the spring force of the buffer spring and acts as an adjusting member at the time when a predetermined ramp portion at which the cam is rotated and the other end of the arm starts opening the valve is received. Abut. Therefore, the other end of the rocker arm comes into contact with the upper end of the valve stem without receiving an impact force, and no striking sound is generated due to the contact.

Further, at the time of this contact, the other end of the rocker arm does not apply an impact force to the valve stem, so that its deformation can be effectively prevented.

Further, since the predetermined lift amount can be obtained while keeping the ramp portion of the cam short, the lift amount of the cam and the push-down amount for pushing down the upper end portion of the valve stem can be relatively matched. . Therefore, the opening / closing timing of the valve can be normally maintained, engine performance can be ensured, and the base circle of the cam can be reduced to ensure downsizing of the engine.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an overhead valve engine equipped with a rocker arm support device according to the present invention. In the figure, a boat-shaped rocker arm 5 having a substantially U-shaped cross section is provided at the top of the overhead valve engine 1, and the rocker arm 5 is provided with a rocker arm support member 3 as will be described later in detail. The pivot member 4, the coil-shaped buffer spring 20 which is an elastic body, and the adjusting nut 27 which is an adjusting member are swingably supported.

On the other hand, the cylinder lock 6 rotatably supports a cam shaft 8 which interlocks with the crankshaft 7. The upper end portion 10a of the push rod 10 interlocking with the cam 9 provided on the camshaft 8 has the above rocker. Arm 5
Is in contact with one end 5a of the. The push rod 10 is vertically displaced by the rotation of the cam 9, whereby the rocker arm 5 can swing. In addition, 11 is a push rod support.

A valve 12 is incorporated in the cylinder block 6 together with a spring 13 and a retainer 14,
The upper end portion 15a of the valve stem 15 is in contact with the other end portion 5b of the rocker arm 5. This valve stem 1
A pushing-up force by the valve spring 13 and a pushing-down force by the rocker arm 5 based on the pushing-up force of the push rod 10 act alternately on the valve 5, so that the valve 12 is opened and closed.
Reference numeral 16 is a piston, 17 is a connecting rod, and 18 is an intake passage.

A rocker arm support member 3 extending in the vertical direction is screwed into the cylinder head 2 in the head cover 19 of the cylinder head 2, and the rocker arm 5 is gently fitted into the rocker arm support member 3. There is. At the center of the rocker arm 5, both ends 5a,
A curved portion 21 that is curved downward from 5b is formed. The curved portion 21 is provided with a through hole 22 through which the rocker arm support member 3 penetrates. The inner diameter of the through hole 22 is selected to be larger than the outer diameter of the rocker arm support member 3, whereby the rocker arm 5 is
Is allowed to swing.

Further, as shown in FIG. 2, the cylindrical pivot member 4 is gently fitted into the rocker arm support member 3 and the adjust nut 27 which is an adjusting member is provided.
Is screwed on. The lower end surface 23 of the pivot member 4 is in sliding contact with the curved portion 21 of the rocker arm 5. The lower end surface 23 and the curved portion 21 are selected to have the same curvature, whereby the rocker arm 5 is kept to swing smoothly. Further, the pivot member 4 includes
A spring accommodating chamber 24 is provided, and this spring accommodating chamber 24
The coil-shaped buffer spring 20 which is an elastic body is housed in the. Both ends of the buffer spring 20 are supported by the spring receiving portion 25 of the pivot member 4 and the adjusting nut 27. This buffer spring 2
0 serves to apply an elastic force to the rocker arm 5 in such a direction that the both end portions 5a and 5b of the rocker arm 5 are always brought into contact with the respective upper end portions 10a and 15a of the push rod 10 and the valve stem 15. . The adjusting nut 27 serves to adjust the elastic force of the buffer spring 20 and is positioned by the fixed nut 28.

The valves 12, rocker arms 5 and push rods 10 are provided for intake and exhaust respectively.

In the above structure, the rocker arm 5 is pushed downward by the spring force of the buffer spring 20 via the pivot member 4, the one end 5a of the rocker arm 5 is brought into contact with the upper end 10a of the push rod 10, and The other end 5b of the rocker arm 5 has an upper end portion of the valve stem 15
15a is brought into contact with the tappet clearance to be zero. Here, in order to keep the valve 12 closed,
The spring force of the valve spring 13 is stronger than that of the buffer spring 20.

When the cam 9 is rotated in this state, the push rod 10
For example, reciprocates in the axial direction with the lift amount shown by the solid line L1 in FIG. 3, and the rocker arm 5 moves in the forward stroke.
Has its one end 5a pushed up.

In the process of pushing up, first, the arm 5 uses the other end 5b as a fulcrum to push up the pivot member 4 against the spring force of the buffer spring 20, and the upper end of the pivot member 4 abuts against the adjusting member 27. Let

Next, after this contact, the arm 5 swings around the lower end surface 23 of the pivot member 4 as a fulcrum, and the other end 5
The upper end 15a of the valve stem 15 is pushed down by b to open the valve 12.

That is, when the cam 9 is rotated and the predetermined ramp portion R1 (FIG. 3) at which the other end 5b of the arm 5 starts opening the valve 12, the upper end of the pivot member 4 is It contacts the adjusting member 27 while receiving the spring force of the buffer spring 20. Therefore, the other end portion 5b of the rocker arm 5 comes into contact with the upper end portion 15a of the valve stem 15 without receiving an impact force, and no striking sound is generated due to the contact.

Further, at the time of this contact, the other end 5b of the rocker arm 5 does not apply an impact force to the hull stem 15, so that the deformation thereof can be effectively prevented.

Further, since the lift amount shown by the solid line L1 can be obtained while keeping the ramp portion R1 of the cam 9 short, the lift amount of the cam 9 (solid line L1) and the upper end portion of the valve stem 15 can be obtained.
It is possible to relatively match the amount of depression of 15a. Therefore, the opening / closing timing of the valve can be normally maintained and the engine performance can be ensured, and the base circle of the cam 9 can be made small to ensure the miniaturization of the engine.

As is clear from the above, even if the push rod 10 extending long between the cylinder head 2 and the cylinder block 6 is made of iron, and the cylinder head 2 and the cylinder block 6 are made of aluminum die casting, It is possible to reliably prevent the increase in tappet clearance as described in the prior art due to the difference in the coefficient of linear expansion between iron and aluminum when the engine is warmed up. As a result, it is possible to prevent a tapping sound from being generated when the rocker arm 5 pushes down the valve stem 15 during engine operation, and it is possible to eliminate the occupant's discomfort caused by the tapping sound.

Further, when the rocker arm 5 is pushed down, it is possible to prevent a large impact force from being applied to the rocker arm 5 due to the action of the buffer spring 20. Therefore, even when the rocker arm 5 manufactured by low-cost sheet metal press molding is used, there is no possibility of deforming the rocker arm 5.

Further, the adjustment of the elastic force of the buffer spring 20 by the adjusting nut 27 screwed to the rocker arm support member 3 can be easily performed only by removing the head cover 19.

Moreover, it is not necessary to preset the tappet clearance in consideration of thermal expansion of the valve stem 15 during warm-up of the engine when the engine is cold. Therefore, the normal opening / closing operation of the valve 12 is maintained even when the engine is cold, and the engine performance is improved.

[Advantage of the Invention] As described above, according to the present invention, since the tappet clearance is prevented from increasing, it is possible to prevent the tapping sound from being generated when the rocker arm pushes down the valve. Further, it is possible to prevent the rocker arm from being deformed because a large impact force is prevented from being applied to the rocker arm when the valve is pushed down. Further, since the valve is normally opened and closed when the engine is cold and warm, the engine performance is maintained high.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view near a rocker arm 5, and FIG. 3 is a relationship between a cam rotation angle and its lift amount for explaining a conventional technique. It is a graph which shows. 1 ... Overhead valve engine, 3 ... Rocker arm support member, 4 ... Pivot member, 5 ... Rocker arm, 5
a, 5b ... Both ends of rocker arm, 9 ... Cam, 1
0 ... push rod, 12 ... valve, 15 ... valve stem, 20 ... elastic body, 27 ... adjusting member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References US Pat. No. 3964455 (US, A) Actual application No. 58-186376 (Actual development No. 60-92708) The specification and the contents of the drawings attached to the application are photographed. Micro film (JP, U) Micro film (JP, U) taken from the contents of the specification and drawings attached to the application for Japanese Patent Application No. 48-62166 (No. 50-9609, Japanese Utility Model)

Claims (1)

[Scope of utility model registration request] 1. A rod-shaped rocker arm support member fixed to the top of an engine, a substantially boat-shaped rocker arm whose central portion is swingably supported and axially movable, and this rocker arm. A cylindrical pivot member that is in axial contact with the upper surface of the support member and is axially movably fitted to the support member,
An adjusting member which is supported at the tip end portion of the supporting member so as to be axially adjustable and regulates the axial movement position of the pivot member, and an elastic body made of a buffer spring in which both ends are brought into pressure contact with the pivot member and the adjusting member, An upper end is in contact with the lower surface of one end of the rocker arm, and a push rod that axially moves by the displacement of the cam to swing the rocker arm, and an upper end is in contact with the lower surface of the other end of the rocker arm, A valve stem in which a spring force is constantly urged in the closing direction of the valve, and the push rod and the valve stem are constantly in contact with the lower surfaces of both ends of the rocker arm by the elastic force of the elastic body, and the valve is Rocker arm support device, configured to buffer the impact force of the pivot member abutting the adjustment member during the opening operation of the rocker arm.