JP2006152911A - Valve train for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a valve come in face contact with a valve bridge to suppress wear and prevent inclination of the valve bridge as far as possible. <P>SOLUTION: In a valve train for an engine, one valve bridge 20 is reciprocated by the rocking of a valve arm 15, and two valves 21 abutted on the valve bridge 20 are operated at the same time. In the valve bridge 20 of a guideless type supported between the valve arm 15 and two valves 21, a contact face 35 of each valve 21 with respect to the valve bridge 20 is formed in a spherical surface in a shape of a recess or projection, and a face 30 to be contact with respect to each valve 21 of the valve bridge 20 is formed in a spherical surface in a shape of projection or recess coming into face contact with a contact face 35 of the valve 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a valve operating mechanism for an engine in which two valves are simultaneously operated by a valve arm via one valve bridge.

  There is an engine of a type in which two intake valves and exhaust valves are provided in one cylinder, one valve bridge is brought into contact with two intake valves or exhaust valves, and two valves are operated simultaneously via the valve bridge by a valve arm. It is known. In this engine, generally, a guide rod separate from the valve bridge is erected on the cylinder head, and the valve bridge is fitted to the guide rod so as to be movable in the axial direction. To be slid. Conventionally, this type of engine has often been employed in relatively large engines.

  However, in recent years, since the adoption of this type is also advanced for small engines, it is desired to reduce the size and weight of the valve operating mechanism. In addition, low cost is desired regardless of size.

  The following Patent Documents 1 to 4 disclose a technique in which the guide rod is omitted as a method for realizing a reduction in size and weight of the valve operating mechanism.

JP 11-280417 A Japanese Patent Laid-Open No. 11-280420 JP 2003-56317 A JP-A-8-170506 JP 2001-152816 A

  Although each said patent document is devised so that a valve bridge can be supported even if a guide rod is abbreviate | omitted, all are inadequate and the following problems still remain, respectively.

  In Patent Documents 1 and 2, a valve bridge and a valve arm are brought into surface contact with an uneven spherical surface, and in Patent Document 3, a push rod is interposed between the valve bridge and the valve arm, and the push rod and the valve bridge are arranged. Are in surface contact with an irregular spherical surface. In this case, since the valve bridge can move freely with the center of the spherical surface as a fulcrum with respect to the valve arm, the valve bridge easily tilts in the direction in which the two valves are juxtaposed, thereby causing a difference in the lift amount of the two valves. There was a risk of engine performance fluctuations. In addition, the valve bridge tends to be inclined in a direction perpendicular to the direction in which the two valves are arranged side by side, and this inclination may cause a bending force to act on the valve and hinder smooth operation.

  Moreover, in patent documents 1-3, the recessed part which has a flat concave bottom face is formed in the lower surface of the both ends of a valve bridge, the upper end part of each valve is fitted to each recessed part, and the upper end surface of a valve is concave. It was formed on a flat surface in surface contact with the bottom surface. For this reason, if the height of the two valves is different due to wear or the like and the valve bridge is tilted, the concave bottom surface and the top end surface of the valve will be in point contact with each other, and there is a problem that they are more easily worn. It was.

  In Patent Documents 4 and 5, concave portions having flat concave bottom surfaces are formed on the lower surfaces of both end portions of the valve bridge, and the upper end portion of the valve is fitted in each concave portion. The upper end of the bulb is formed in a spherical shape and is in point contact with the concave bottom surface. For this reason, there has been a problem that the contact pressure between the valve and the valve bridge is increased, resulting in severe wear. Further, there is a problem that rattling is likely to occur between the valve and the valve bridge, and the valve bridge tends to be inclined when the sliding resistances of the two valves are different.

  The present invention has been made in view of the above problems, and its object is to suppress wear by making the contact between the valve and the valve bridge into a surface contact and to suppress the inclination of the valve bridge as much as possible. It is. Further, the two contact surfaces of the valve bridge are adapted to the positions of the two valves so that the surface contact state can be maintained.

  The invention according to claim 1 is a valve operating mechanism for an engine in which one valve bridge is reciprocated by swinging a valve arm, and two valves in contact with the valve bridge are operated simultaneously. When the bridge is of a guideless type supported between the valve arm and the two valves, the contact surface of each valve with respect to the valve bridge is formed as a concave or convex spherical surface. A contact surface with respect to each valve is formed as a convex or concave spherical surface that is in surface contact with the contact surface of the valve.

  The invention according to claim 2 is the invention according to claim 1, wherein the valve arm is provided with a pressing surface, and the valve bridge is provided with a pressed surface with which the pressing surface abuts, and the pressing surface or the pressed surface One of the surfaces is a flat surface, the other is a cylindrical surface, the pressing surface and the pressed surface are in line contact with each other, and the direction of the contact line between the flat surface and the cylindrical surface is parallel to the two valves. It is set in a direction that intersects the direction.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the interval between the two abutted surfaces of the valve bridge is provided so as to be expandable / contractible.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the valve bridge includes a main body portion and a slider provided so as to be movable in the juxtaposition direction of the two valves with respect to the main body portion. One contacted surface is formed on the slider.

  According to a fifth aspect of the present invention, in the invention of the fourth aspect, the frictional resistance between the body portion of the valve bridge and the slider is greater than the frictional resistance between the pressed surface of the valve bridge and the pressing surface of the valve arm. Has also been enlarged.

  According to the first aspect of the present invention, the contact surfaces of the two valves and the contacted surface of the valve bridge can always be in a surface contact state, and wear can be suppressed. In addition, the backlash between the two can be reduced and the inclination of the valve bridge can be prevented.

  According to invention of Claim 2, it can prevent that a valve bridge inclines in the direction orthogonal to the parallel arrangement direction of two valves.

  According to the invention of claim 3, the interval between the contact surfaces of the valve bridge can be changed according to the interval between the contact surfaces of the two valves. For this reason, even when the heights of the two valves are different or when the valve bridge is thermally expanded, the surface contact between the contact surface of the valve and the contacted surface of the valve bridge can be maintained. .

  According to the invention of claim 4, the invention of claim 3 can be suitably realized.

  According to the invention of claim 5, the reciprocating motion of the valve bridge by the valve arm can be smoothly performed, and the movement of the slider due to the reciprocating motion of the valve bridge is suppressed by the frictional resistance between the slider and the main body. . For this reason, two valves can be operated simultaneously while keeping the posture of the valve bridge constant without changing the relative positional relationship between the valve and the valve bridge.

  FIG. 1 is a front sectional view of an engine valve mechanism according to an embodiment of the present invention. The engine 10 is a four-valve engine having two intake valves and an exhaust valve in one cylinder. A cylinder head 11 is fastened to the upper portion of the cylinder block with a bolt or the like, and a cover 12 is fastened to the upper side of the cylinder head 11.

  A valve arm chamber 13 is formed in the cover 12. A valve arm shaft 14 is installed in the valve arm chamber 13, and a valve arm 15 is swingably supported on the valve arm shaft 14. An adjustment screw 16 is screwed to one end of the valve arm 15, and the upper end of the push rod 17 is connected to the lower end of the adjustment screw 16 by a ball joint. The push rod 17 passes through the cylinder head 11 and extends into the lower crankcase, and a lower end thereof is in contact with the cam 18 via a tappet or the like.

  A pressing portion 19 is formed at the other end of the valve arm 15, and a valve bridge 20 is disposed below the pressing portion 19. Two valves 21 (intake valves or exhaust valves) are arranged in parallel below the left and right sides (both sides in the longitudinal direction) of the valve bridge 20. Therefore, the valve bridge 20 is disposed so as to straddle the two valves 21.

  The valve 21 has a valve rod 22 supported by the cylinder head 11 so as to be slidable up and down, and a valve body 23 provided at the lower end of the valve rod 22, and is attached to the upper portion of the valve rod 22. It is urged upward by a compression spring 25 interposed between the spring seat 24 and the upper surface of the cylinder head 11, thereby closing the valve body 23. The upper end of the valve rod 22 is in contact with the lower portions of the left and right sides of the valve bridge 20.

  The valve bridge 20 of the present invention is a guideless type that is supported between the valve 21 and the valve arm 15 without being guided by a guide member.

  2 is a front view of the main part of the valve operating mechanism, FIG. 3 is a sectional view taken along the line III-III in FIG. 2, and FIG. The pressing portion 19 of the valve arm 15 has a downward pressing surface 26. The pressing surface 26 is formed in a cylindrical surface centered on an axis parallel to the valve arm axis. On the other hand, an upward pressed surface 27 is formed on the upper left and right center surfaces of the valve bridge 20, and the pressed surface 27 is a flat surface. The pressing surface 26 is in contact with the pressed surface 27, and both are in line contact with each other.

  On both the left and right sides of the valve bridge 20, contacted portions 28 for the valve 21 are provided. The contacted portion 28 has a concave portion 29 that is recessed upward from the lower surface of the valve bridge 20, and the bottom surface (contacted surface 30) of the concave portion 29 is a spherical surface that is recessed in a concave shape.

  One of the left and right (left) contacted portions 28 is configured to be movable in the left-right direction. That is, as shown in FIG. 5, the valve bridge 20 includes a main body portion 31 and a slider 32, and a left and right groove (guide portion) 33 is formed on the lower surface of the main body portion 31. The slider 32 is fitted in the groove 33 so as to be slidable in the left-right direction. The slider 32 forms a left contacted portion 28, and a recess 29 is formed on the lower surface of the slider 32. The groove 33 is open to the left end side of the main body 31.

  The left and right other (right) contacted portion 28 is formed directly with respect to the main body portion 31.

  An upper end portion of the valve rod 22 of the valve 21 is a contact portion 34 with respect to the valve bridge 20, and the corresponding contact portion 34 can be fitted into the recess 29. The tip surface (contact surface 35) of the contact portion 34 is a convex spherical surface that matches (same diameter as) the spherical surface of the contacted surface 30. Are in surface contact.

  The outer diameter of the lower end portion (opening portion) of the recess 29 is slightly larger than the outer diameter of the contact portion 34, and the recess 29 is fitted between the recess 29 and the contact portion 34. Is formed with a gap t.

[Effects of this embodiment]
In the above configuration, as shown in FIG. 1, when the cam 18 is rotated by the crankshaft of the engine 10, the valve arm 15 swings about the valve arm shaft 14 via the push rod 17, and the valve arm 15 The pressing portion 19 reciprocates the valve bridge 20. The two valves 21 slide downward by being pressed by the valve bridge 20 against the compression spring 25 and open the valve body 23.

  At this time, as shown in FIG. 2, the contacted surface 30 of the valve bridge 20 and the contact surface 35 of the valve 21 are in a surface contact with a spherical surface, so that they are compared with the case of point contact or line contact. The contact pressure is reduced and wear is suppressed. Further, since the backlash between the valve bridge 20 and the valve 21 is reduced by the surface contact, the followability of the valve 21 with respect to the valve bridge 20 is improved, and the valve bridge 20 is inclined in the direction in which the valves are juxtaposed (arrow A). Inclination in the direction orthogonal to the valve juxtaposition direction (arrow B in FIG. 3) can be prevented.

  However, since a radial gap t is formed between the valve bridge 20 and the valve 21, a slight inclination of the valve bridge 20 is allowed, and no excessive force is applied to the valve 20 when it is inclined. It is like that. Even if the valve bridge 20 is slightly inclined, the surface contact state can be maintained because of the surface contact by the spherical surface.

  When the temperature rises due to the operation of the engine 10, the valve bridge 20 may thermally expand, and the interval between the two abutted surfaces 30 may increase. In this case, since one contacted surface 30 is formed on the slider 32, the slider 32 slides left and right so as to fit the distance between the two valves 21, so that the contact surface 35 of the valve 21. And the contacted surface 30 of the valve bridge 20 are maintained.

  In addition, when the heights of the upper ends of the two valves 21 are different due to wear or the like, the distance between the upper ends fluctuates. In this case as well, the slider 32 slides and the distance between the upper ends of the valves 21 is reduced. The distance between the contact surfaces 30 can be adapted.

  As shown in FIG. 4, the valve arm 15 and the valve bridge 20 are arranged in a slightly inclined relationship in plan view, and the cylindrical pressing surface 26 of the valve arm 15 and the pressed surface 27 of the valve bridge 20. The direction of the line contact (the direction of the contact line) intersects the direction in which the two valves 21 are juxtaposed. As a result, the valve bridge 20 is prevented from tilting (falling) in a direction orthogonal to the valve juxtaposition direction.

  The friction coefficient between the pressing surface 26 of the valve arm 15 and the pressed surface 27 of the valve bridge 20 is smaller than the friction coefficient between the slider 32 and the main body 31. For this reason, the movement (sliding) of the contact position between the pressing surface 26 and the pressed surface 27 accompanying the swing of the valve arm 15 becomes smooth. On the other hand, the slider 32 has a large frictional resistance with respect to the main body 31, so that the slider 32 does not move with respect to the main body 31 due to the pressing operation of the valve bridge 20 by the valve arm 15, and the relative relationship between the valve bridge 20 and the valve 21. The positional relationship does not change. Therefore, the valve bridge 20 reciprocates with a constant posture, and there is almost no difference between the lift amounts of the two valves 21.

[Other Embodiments]
The present invention is not limited to the embodiment described above, and can be appropriately changed in design. For example, the contact surface 35 of the valve 21 can be formed into a concave spherical surface, and the contacted surface 30 of the valve bridge 20 can be formed into a convex spherical surface. Moreover, the pressing surface 26 of the valve arm 15 can be formed into a flat surface, and the pressed surface 27 of the valve bridge 20 can be formed into a cylindrical surface.

  In the above embodiment, the slider 32 of the valve bridge 20 is fitted in the groove 33 of the main body 31. However, a convex rail is formed on the main body 31, and the groove 33 that fits on the rail is formed on the slider side. May be. Further, although the slider 32 is provided as one contacted portion 28, it can be provided as both the contacted portions 28. However, in this case, since both the abutted portions 28 move with respect to the main body portion 31 and positioning becomes difficult, it is preferable that only one abutted portion 28 is constituted by the slider 32. .

  A configuration other than the linear movement by the slider 32 may be employed as a configuration that allows the interval between the two contact surfaces 30 of the valve bridge 20 to be freely expanded and contracted.

It is front sectional drawing of the valve mechanism of the engine 10 concerning embodiment of this invention. It is a front view of the principal part of a valve operating mechanism. FIG. 3 is a sectional view taken along line III-III in FIG. 2. FIG. 4 is a view taken along arrow IV in FIG. 2. It is a disassembled perspective view of the one end part of a valve bridge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 15 Valve arm 19 Press part 20 Valve bridge 21 Valve 26 Press surface 27 Pressed surface 30 Touched surface 31 Body part 32 Slider 35 Contact surface

Claims (5)

1. A valve operating mechanism for an engine in which one valve bridge is reciprocated by swinging a valve arm and two valves in contact with the valve bridge are operated simultaneously. In what is a guideless type supported between two valves,
The contact surface of each valve with respect to the valve bridge is formed into a concave or convex spherical surface, and the contact surface with respect to each valve of the valve bridge is formed into a convex or concave spherical surface that is in surface contact with the contact surface of the valve. The valve operating mechanism of the engine, characterized in that   The valve arm is provided with a pressing surface, the valve bridge is provided with a pressed surface with which the pressing surface abuts, one of the pressing surface or the pressed surface is a flat surface, and the other is a cylindrical surface. The surface and the pressed surface are in line contact with each other, and the direction of the contact line between the flat surface and the cylindrical surface is set in a direction intersecting the parallel arrangement direction of the two valves. Engine valve mechanism.   The valve operating mechanism for an engine according to claim 1 or 2, wherein an interval between two contact surfaces in the valve bridge is provided so as to be freely expandable and contractible.   The valve bridge includes a main body portion and a slider provided so as to be movable in the direction in which the two valves are juxtaposed with respect to the main body portion, and one contacted surface is formed on the slider. The valve operating mechanism for an engine according to claim 3. 5. The valve operating mechanism for an engine according to claim 4, wherein the frictional resistance between the main body of the valve bridge and the slider is larger than the frictional resistance between the pressed surface of the valve bridge and the pressing surface of the valve arm. .

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