Valve train mechanism for overhead valve-type engine

Abstract

The present invention provides a valve train mechanism for an overhead valve-type engine provided with a highly versatile adjusting mechanism. Provided is the valve train mechanism (1) for an overhead valve-type engine, the valve train mechanism comprising: a push rod (4) that moves vertically with the rotation of a cam (2); a rocker arm (3) that is rotatably supported by being inserted into a shaft (3b), the rocker arm (3) being configured such that the vertical movement of the push rod (4) is transmitted to one end (3d) and the rocker arm (3) reciprocally oscillates to open and close an engine valve (5) at the other end (3a); a lash adjuster (10) that is swingably supported on a recess (3e) provided at the one end (3d) of the rocker arm (3) and transmits the vertical motion of the push rod (4) to the one end (3d) of the rocker arm; and an adapter (30) that is attached to the lash adjuster (10) and is interposed between the lash adjuster (10) and the push rod (4), wherein the adapter (30) is attached to and integrated with a sliding part (14) of the lash adjuster (10) at an upper part, and is supported at a lower part (31) by an upper end part (31) of the push rod, and the lash adjuster (10) transmits the vertical motion of the push rod (4) to the rocker arm (3) via an adapter (30) and adjusts the valve clearance.

Description

Overhead valve engine valve train

[0001] The present invention relates to a valve train for an overhead valve type engine.

[0002] In an overhead valve (OHV) engine, such as that described in Patent Document 1, a rocker arm is swingably supported on a rocker shaft, one end of the rocker arm is provided with a valve abutment that abuts against the valve, and the other end is threadedly fitted with an adjust screw that abuts against the upper end of a push rod. When the push rod moves up and down due to the rotation of a cam, the rocker arm swings around the rocker shaft as a fulcrum, opening and closing the valve via the valve abutment. The lower surface of the adjust screw abuts against a bowl-shaped joint provided at the upper end of the push rod, transmitting the up and down movement of the push rod. The adjust screw is an adjustment mechanism for the valve train, and its position is adjusted by threading the adjust screw, thereby adjusting the valve clearance.

[0003] JP 2008-128151 A

[0004] However, the contact surface between the adjustment mechanism and the push rod is a spherical contact structure, and because the shape and dimensions vary depending on the engine model, it is not possible to use a general-purpose part. A dedicated part must be designed and manufactured for each engine model, which is costly and makes quality control difficult.

[0005] The present invention has been made in view of this, and provides a valve train for an overhead valve engine equipped with a highly versatile adjustment mechanism.

[0006] In order to solve the above problems, in one aspect of the present invention, a valve train for an overhead valve engine is configured comprising: a push rod that moves up and down in response to rotation of a cam; a rocker arm that is inserted into a shaft and supported rotatably, and has one end to which the up and down movement of the push rod is transmitted, causing the rocker arm to swing back and forth and open and close an engine valve at the other end; a lash adjuster that is supported rotatably in a recess provided in the one end of the rocker arm and transmits the up and down movement of the push rod to the one end of the rocker arm; and an adapter that is attached to the lash adjuster and interposed between the lash adjuster and the push rod, wherein an upper part of the adapter is attached to and integrated with a sliding portion of the lash adjuster and a lower part is supported by the upper end of the push rod, and the lash adjuster transmits the up and down movement of the push rod to the rocker arm via the adapter and adjusts the valve clearance.

[0007] According to this aspect, the lash adjuster is pivotally supported on one end of the rocker arm and slides as the cam rotates, thereby adjusting the rocker arm clearance to zero by the lash adjuster. Furthermore, because the above-described movement of the lash adjuster is performed via the adapter, the position of the lash adjuster can be adjusted by the adapter. This eliminates the need to adjust the connection to the cam, the position, and other aspects on the lash adjuster side, which has a complex configuration. The adapter allows the lash adjuster to be used with other engine configurations. Because it is the adapter that slides against the cam, even if the adapter wears due to sliding against the cam, it is only necessary to replace the adapter. The same type of lash adjuster can be used in a variety of engines. This provides a valve train for an overhead valve engine equipped with a highly versatile adjustment mechanism.

[0008] In one embodiment, the adapter and the upper end of the push rod are supported by a joint connection in which one end is configured as a convex portion and the other as a concave portion, and the convex portion is rotatably inserted and supported inside the concave portion. The bottom surface of the adapter that abuts the push rod is surface-treated to reduce wear with the push rod. According to this embodiment, the wear-reducing surface treatment applied to the adapter reduces friction between the cam and the adapter. This also reduces resistance in the valve train and improves engine performance. Furthermore, the ease of adapter replacement also improves maintenance of the engine and valve train.

[0009] In one embodiment, the adapter has a groove formed on the bottom surface for retaining oil. By retaining oil in the groove, friction is further reduced and the reduced friction can be maintained for a longer period of time.

[0010] In one aspect, the lash adjuster is configured so that the sliding portion is inserted into the recessed engaging portion of the adapter for assembly, an outer peripheral groove is formed on the outer surface of the sliding portion of the lash adjuster, and an inner peripheral groove is formed on the inner surface of the engaging portion, and the adapter is fixed to the sliding portion by an engaging member that fits into the outer peripheral groove and the inner circumferential groove. According to this aspect, the above configuration makes it easy to engage and disengage the adapter and to replace the adapter, improving the maintainability of the valve train.

[0011] As is clear from the above description, it is possible to provide a valve train for an overhead valve engine equipped with a highly versatile adjustment mechanism.

[0012] 1 is a partial cross-sectional view showing an embodiment of a valve train of the present disclosure; FIG. 2 is a cross-sectional view of part A of FIG. 1, showing an enlarged view of a lash adjuster and an adapter; FIG. 3 is a view showing a C-clip that engages the adapter and the lash adjuster; FIG. 4 is a view showing a modified example of the adapter and lash adjuster; FIG. 5 is a view showing a modified example of the valve train;

[0013] Specific embodiments of the present invention will be described below with reference to the drawings. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. In addition, in the following description of the embodiments and modifications, the same components are designated by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0014] 1 is a partial cross-sectional view of a valve mechanism 1 according to the configuration of the present disclosure. Note that in each drawing, directions are described based on the axial direction of the shaft that pivotally supports the rocker arm, with this being the front-to-rear direction (front: rear = toward the front of the paper: toward the back of the paper = Fr:Re), the horizontal direction perpendicular to the axis of the rocker arm being the left-to-right direction (right: left = Ri:Le), and the vertical direction being the up-down direction (up: down = Up:Lo).

[0015] 1 is a valve train for an engine valve mounted on an overhead valve (OHV) engine. The valve train 1 includes a cam 2, a rocker arm 3, a push rod 4, a pair of engine valves 5, a pair of valve springs 7, a valve bridge 11, a valve bridge shaft 12, a lash adjuster 10, and an adapter 30.

[0016] The cam 2, rocker arm 3, engine valve 5, and valve bridge 11 are each supported inside a cylinder head 8. The atmosphere inside 8a of the cylinder head 8 contains oil.

[0017] The rocker arm 3 is inserted onto a shaft 3b of a base 3c held by the cylinder head 8, and is supported so as to be rotatable about the shaft 3b. A lash adjuster 10 is held at one end of the rocker arm 3 (the left end 3d in FIG. 1).

[0018] Lash adjuster 10 is disposed with a portion thereof protruding from the bottom surface of rocker arm 3. Lash adjuster 10 is configured to be extendable and contractible, changing its overall length and adjusting the clearance to zero. The downward protruding portion of lash adjuster 10 is a sliding portion (body 14, described below) of lash adjuster 10, which is configured so that the amount of protrusion can be changed, and an adapter 30 is attached to the lower end.

[0019] The push rod 4 has a bowl-shaped joint 4b at its upper end and a valve lifter 4a at its lower end. The joint 4b at the upper end of the push rod 4 abuts against a convex semispherical adapter 30 to hold it inside, while the valve lifter 4a at the lower end abuts against the outer peripheral surface of the cam 2 so as to be slidable in the vertical direction.

[0020] As the cam 2 rotates, the push rod 4 moves up and down, and the adapter 30 and lash adjuster 10 supported on the upper end of the push rod 4 transmit the up and down movement of the push rod 4, moving the left end 3d of the rocker arm 3 up and down, causing the rocker arm 3 to swing back and forth around the axis 3b, and the other end of the rocker arm 3 (the right end 3a in Figure 1) to reciprocate up and down.

[0021] The valve bridge 11 has legs 11c extending vertically and arms 11a extending laterally. The tip of a rod-shaped valve bridge shaft 12 that protrudes and passes through a vertical through-hole inside the leg 11c is press-fitted into an engaging recess 8b in the cylinder head 8 and fixed therein. This allows the valve bridge 11 to move up and down along the valve bridge shaft 12. A spiral groove that acts as an oil supply passage is formed in the valve bridge shaft 12, allowing the valve bridge 11 to move up and down smoothly along the valve bridge shaft 12.

[0022] The pair of engine valves 5 are identical valves each having a head portion 5b and a stem portion 5a, and the base end portion 5c of each stem is urged against a recessed portion on the bottom surface of the arm portion 11a of the rocker arm 3 by a pair of valve springs 7 held in the cylinder head 8. The valve bridge 11 is urged against the right end portion 3a of the rocker arm 3 by the valve springs 7 via the engine valves 5.

[0023] The head portion 5b of the engine valve 5 closes the intake passage 9 (or exhaust passage) due to the biasing force of the valve spring 7. When the right end portion 3a of the valve bridge 11 descends due to the rotation of the cam 2, it descends together with the engine valve 5, opening the valve and supplying the air-fuel mixture in the intake passage 9 (or exhaust passage) into the combustion chamber 8c (or exhausting it in the case of an exhaust passage). As the cam 2 continues to rotate, the valve bridge 11 rises together with the engine valve 5 due to the biasing force of the valve spring 7, closing the valve.

[0024] (Lash Adjuster) Figure 2 is an enlarged cross-sectional view of part A in Figure 1. First, we will explain the lash adjuster 10. The lash adjuster 10 has a plunger 13, a body 14, a plunger spring 15, a check ball 16, a check ball spring 17, and a ball cage 19.

[0025] The plunger 13 is cylindrical with a bottom, has a first oil reservoir 13a on the inside, has a hole 13b on the bottom, and has a ball cage 19 fixed below the bottom. The body 14 is also cylindrical with a bottom, and holds the plunger 13 inside so that it can slide freely with a plunger spring 15 formed as a compression spring provided on the bottom. A second oil reservoir 18 is formed between the plunger 13 and the body 14.

[0026] A cylindrical recess 3e with a top surface is formed in the bottom surface of the left end 3d of the rocker arm 3, for mounting a lash adjuster 10. The lash adjuster 10 is inserted and held in the recess 3e in a state where it can slide freely. The lash adjuster 10 is inserted with its body 14 facing downward, and a portion of the body 14 protrudes from the bottom surface of the left end 3d. The plunger 13 is urged by a plunger spring 15 toward the top surface 3f of the cylindrical recess 3e with a top surface.

[0027] The check ball 16 is urged against the inner edge 13 c of the hole 13 b in the bottom of the plunger 13 by a check ball spring 17 held on the bottom surface of the ball cage 19 inside the ball cage 19 .

[0028] An oil supply passage 3h is formed in the center of the shaft 3b, extending in the axial direction. Furthermore, an oil supply passage 3g communicating with the oil supply passage 3h is formed inside the rocker arm 3. The oil supply passage 3g extends horizontally toward the left end 3d of the rocker arm 3, communicates with the cylindrical recess 3e with a top face, and opens to the left side of the rocker arm 3. Because the plunger 13 is biased against the top face 3f of the recess 3e, the oil supply passage 3g is connected only to a portion of the top face 3f and continues to the first oil reservoir 13a.

[0029] The check ball 16 closes the hole 13b when the cam 2 rotates, pushing up the push rod 4 and lowering the left end 3d of the rocker arm 3, and when the cam 2 further rotates and the push rod 4 stops rising, the check ball 16 opens the hole 13b based on the hydraulic pressure difference generated between the first oil reservoir chamber 13a and the second oil reservoir chamber 18. With the hole 13b open, the plunger 13 receives the biasing force of the plunger spring 15 and lowers the body 14.

[0030] In this embodiment, an adapter 30 is attached to the lower end of the body 14 , and the adapter 30 is connected to the push rod 4 .

[0031] As described above, when the plunger 13 of the lash adjuster 10 lowers the body 14 due to the biasing force, the adapter 30 is pushed down, eliminating the clearance that occurs between the tip of the adapter 30 and the upper end of the push rod 4. The body 14 is the sliding part of the lash adjuster 10, and slides up and down within the recess 3e to change the amount of protrusion from the bottom surface of the rocker arm 3.

[0032] (Adapter) The adapter 30 is attached to the body 14 , and the push rod 4 and the lash adjuster 10 are connected via the adapter 30 .

[0033] The adapter 30 is composed of an upper and lower integrated engaging portion 31 that engages with the lower portion of the body 14 that protrudes from the rocker arm 3, and an abutting portion 32 that connects to the push rod 4. The engaging portion 31 is fixed to the lower end of the body 14, so that the body 14 and the adapter 30 move up and down as a unit.

[0034] In this embodiment, the body 14 and the engaging portion 31 are integrally engaged by a C-clip 40, which is an engaging member. The engaging portion 31 has a cylindrical, bottomed shape and is provided with an inner circumferential groove 31a on its inner surface. Similarly, the body 14 has a corresponding outer circumferential groove 14a on its outer surface.

[0035] When the C-clip 40 is fitted into the outer peripheral groove 14a, the C-clip 40 becomes a circular convex portion protruding from the outer peripheral surface of the body 14. The engaging portion 31 is inserted into the body 14 from below, climbing over the C-clip 40 protruding from the outer peripheral surface of the body 14, and the C-clip 40 is fitted into the inner peripheral groove 31a, whereby the C-clip 40 fits into the inner peripheral groove 31a and the outer peripheral groove 14a, and the engaging portion 31 is fixed to the body 14.

[0036] Fig. 3 shows a C-clip 40. As shown in Fig. 3, the C-clip 40 is made by forming a wire rod into a generally C-shape, with a notch 40a provided in a portion of the generally circular shape. The C-clip 40 is a C-clip formed into a wavy, C-shape by deformation processing in which the base circle is repeatedly curved inward and outward in the circumferential direction. In this embodiment, because the radius of curvature of the wavy curve is large, the outer shape of the C-clip 40 is a generally polygonal shape with rounded corners.

[0037] The C-clip 40 is a retaining member that, when attached to the body 14, prevents the engaging portion 31 from coming off the body 14. The C-clip 40 firmly secures the adapter 30 to the body 14, but if the adapter 30 wears out due to wear or the like and you want to replace it with a new adapter 30, you can remove the adapter 30 from the body 14 by forcibly pulling it out. With the above configuration, the adapter 30 is detachable from the body 14.

[0038] Because the C-clip 40 is configured in a wavy shape, it is easier to deform than a typical C-clip without a wavy shape, making it easier to fit into the outer circumferential groove 14a of the body 14. Furthermore, the curved portion of the C-clip 40 that protrudes outward protrudes more than conventional clips, making it more difficult for the body 14 to fall off.

[0039] The bottom surface 32a of the abutment portion 32 of the adapter 30 is configured as a downwardly convex spherical shape. The bowl-shaped joint portion 4b of the push rod 4 connected to the abutment portion 32 is a recessed portion that opens upward, and its inner surface is configured as a spherical shape that opens upward and has a larger diameter than the bottom surface 32a. The abutment portion 32 is inserted into the inside of the joint portion 4b and is supported rotatably (joint connection structure). The spherical bottom surface 32a abuts and is supported against the spherical joint portion 4b, and the reduced friction due to the spherical shape of both surfaces (spherical joint connection structure) reduces wear due to contact.

[0040] The bottom surface 32a of the contact portion 32 of the adapter 30 is subjected to a surface treatment for reducing friction, such as a diamond-like carbon coating (DLC coating).

[0041] Furthermore, a lubricating oil groove 32b is formed in the bottom surface 32a. The groove 32b is formed by cutting out a portion of the bottom surface 32a along a straight line that passes through the center of the circle of the bottom surface 32a when viewed from the bottom. By forming the groove 32b, oil present in the atmosphere inside the cylinder head 8 adheres to the adapter 30 and remains in the groove 32b. The oil is also retained in the bowl-shaped joint portion 4b, and the oil reduces frictional resistance between the bottom surface 32a and the joint portion 4b.

[0042] The frictional resistance between the bottom surface 32a and the coupling portion 4b that come into contact during coupling connection is reduced, suppressing wear on the adapter 30. This extends the life of the adapter 30, extending the replacement interval and improving maintainability. Furthermore, by reducing the frictional resistance with the cam 2, the resistance value of the valve train 1 is also reduced, improving engine performance.

[0043] (Operation and Effect) By attaching the adapter 30 to the lash adjuster 10, it is the adapter 30, not the lash adjuster 10, that abuts against and is connected to the push rod 4. The push rod 4 is connected to the lash adjuster 10 via the adapter 30, and moves the left end 3d of the rocker arm 3 up and down.

[0044] In the past, when an adjust screw with a pivot at the bottom threaded onto a rocker arm and a joint connected to the upper end of the push rod and the pivot, not only the rocker arm but also the adjust screw (especially the shape of the pivot) had to be designed depending on the shape and form of the push rod (the shape and length of the joint, etc.), and different specifications had to be prepared for each engine.Furthermore, if the push rod abuts not on a pivot but on a lash adjuster with a complex structure, the design becomes even more complicated, and all different specifications must be designed, produced, and managed, which increases costs.

[0045] By using the adapter 30, parts other than the adapter 30 can be shared. This allows a general-purpose part to be used for a lash adjuster, which has a complex structure but also provides the advantage of clearance adjustment. This eliminates the need to prepare all parts as dedicated parts for multiple specifications, which is advantageous in terms of cost and quality control in design and production. The adapter 30 functions as a highly versatile adjustment mechanism, increasing the versatility of the valve train 1.

[0046] The contact surface with the push rod is subject to severe wear due to sliding resistance, and adjustments are frequently required during engine operation. In this embodiment, a low-friction coating is applied only to the bottom surface 32a, which is the contact surface with the joint portion 4b, which is advantageous in terms of cost. Furthermore, the above configuration reduces wear caused by sliding of the adapter 30 with the push rod, thereby reducing the frequency of engine maintenance. Because it is the adapter 30 that wears, even if the adapter 30 reaches its service limit due to wear, the C-clip 40 can be removed and replaced with a new adapter 30. The adapter 30 can be fitted into the lash adjuster 10 for integration, making assembly easy.

[0047] Furthermore, since the lash adjuster 10 can be incorporated into the left end 3d of the rocker arm 3 that is slid by the cam 2 to adjust the valve clearance, there is no need to place a lash adjuster at the right end 3a where the engine valve 5 is located. The added height due to the placement of the lash adjuster 10 can be accommodated by shortening the push rod 4, so there is no need to change the height of the entire valve train, and this actually contributes to making the valve train 1 more compact.

[0048] (Modifications) The configuration of the present disclosure is not limited to the above. For example, the method of fixing the adapter 30 to the lash adjuster 10 is not limited to using the C-clip 40. Another example of a method of fixing the two will be described using FIG. 4. FIGS. 4(A) to 4(F) show the adapter 30 and modifications of the fixing method. Note that, for the lash adjuster, only the body to which the adapter is fixed is shown, and other parts are omitted. Note that parts with similar configurations are assigned the same reference numerals, and redundant explanations will be omitted as appropriate.

[0049] 4A is fixed to the bottom of the body 14 using a retainer 140. The engaging portion 131 of the adapter 130 is formed in a disk shape, and the top diameter of the engaging portion 131 matches the bottom diameter of the body 14. The retainer 140 has a cylindrical shape with a bottom, and a hole is formed in the bottom surface through which the abutment portion 32 is inserted.

[0050] When the top surface of the adapter 130 is brought into contact with the bottom surface of the body 14 and the retainer 140 is forcibly pushed in from below, the lower part of the body 14 and the engaging portion 131 are crimped together by the peripheral side surface of the retainer 140. This integrates the adapter 130 and the body 14. A recess is formed around the outer peripheral side surface of the lower part of the body 14, and a reduced diameter portion recessed inward is formed on the peripheral side surface of the retainer 140, and it is preferable to configure it so that the reduced diameter portion of the retainer fits into the recess of the body to prevent it from coming loose.

[0051] The retainer 140 can be removed by forcibly pulling it out. Removing the retainer 140 releases the connection between the adapter 130 and the body 114. By using the retainer 140 as an engaging member, the adapter 130 can be detachably fixed to the body 114.

[0052] 4B, the inner diameter of the engaging portion 231 is smaller than the outer diameter of the body 14. An air vent hole 239 that communicates with the outside air is provided on the bottom surface of the engaging portion 231, and the adapter 230 is fixed to the body 14 by forcibly pressing the adapter 230 into the body 14 from below.

[0053] 4C is screwed to a body 14′ that has a female screw hole provided on the bottom surface of the body 14. An insertion hole corresponding to the female screw hole is formed in an engagement portion 331 of the adapter 30, and a bolt BT is inserted through the insertion hole and threaded into the female screw hole, thereby screwing the adapter 330 to the body 314.

[0054] The adapter 430 shown in FIG. 4D is dropped into the body 14 in a heated state and is shrink-fitted.

[0055] The adapter 530 shown in FIG. 4E is formed so that the upper surface of the engagement portion 531 matches the shape of the bottom surface of the body 14, and is adhered to the bottom surface of the body 14 with adhesive GL.

[0056] 4(F), the upper end of the contact portion with the body 14 is brazed and fixed with solder S. The joining of the two is not limited to brazing using an alloy as an adhesive, and may be welding.

[0057] The adapters that engage with the body using engaging parts such as the C-clip 40, the retainer 140, and the bolt BT are each removably fixed to the body. The engaging members and the detachable configuration are not essential components, and as shown above, the adapter may be configured without using an engaging member, or may be configured to be completely and irremovably fixed to the body.

[0058] Figure 5 shows another modified example. Figure 5 corresponds to Figure 2. Valve train 101 shown in Figure 5 has the same configuration as valve train 1, except that push rod 704 is used instead of push rod 4, and adapter 730 is used instead of adapter 30.

[0059] The adapter 730 is formed by vertically integrating an upper engaging portion 31 and a lower abutting portion 732. The body 14 and the engaging portion 31 are engaged and integrated by a C-shaped clip 40.

[0060] The joint 704b provided at the upper end of the push rod 704 has an upwardly convex spherical shape. The contact portion 732 of the adapter 730 is formed in a bowl shape that opens downward, and the bottom surface 732a, which is the inner surface of the bowl, has a downwardly open concave spherical shape. The bottom surface 732a is inserted into and contacts the joint 704b, and the adapter 730 is rotatably supported by the joint 704b.

[0061] The bottom surface 732a, like the bottom surface 32a, is treated to reduce friction. The bottom surface 732a is treated with a surface treatment such as DLC coating, and a lubricant groove 732b is formed therein. The lubricant groove 732b has a hole formed in the most protruding ceiling portion. The shape of the lubricant groove provided on the contact surface of the adapter with the push rod is not limited to the aforementioned shape, but may be circular or rectangular, or multiple grooves may be provided. The formation of the lubricant groove allows oil present in the atmosphere inside the cylinder head to remain on the bottom surface 732a, reducing the frictional resistance between the bottom surface 732a and the joint portion 704b.

[0062] In this way, the joint connection between the adapter 730 and the push rod 704 has the opposite concave and convex shape to that of the adapter 30 and the push rod 4. The joint portion provided at the upper end of the push rod is either convex or concave. Whether the joint portion of the push rod is convex or concave, by using an adapter, the rocker arm 3 and lash adjuster 10 can be used as is. The spherical joint configuration, in which the contact surfaces of both are spherical, reduces resistance when the two slide together.

[0063] The above describes preferred embodiments of the present invention, but the above embodiments are merely examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention.

[0064] DESCRIPTION OF SYMBOLS 1: Valve train 2: Cam 3: Rocker arm 3a: Right end (one end of rocker arm) 3b: Shaft 3d: Right end (the other end of rocker arm) 3e: Recess (recess in rocker arm) 4: Push rod 4b: Joint portion (upper end of push rod) 5: Engine valve 10: Lash adjuster 14: Body (sliding portion of lash adjuster) 14a: Outer peripheral groove 30: Adapter 31: Engagement portion 31a: Inner peripheral groove 32: Contact portion 32a: Bottom surface (bottom surface of adapter) 32b: Groove 40: C-clip (engagement member) 101: Valve train

Claims

1. A valve train for an overhead valve engine comprising: a push rod that moves up and down in accordance with the rotation of a cam; a rocker arm that is inserted into a shaft and supported rotatably, the up and down movement of the push rod being transmitted to one end thereof, causing the rocker arm to swing back and forth and open and close an engine valve at the other end; a lash adjuster that is supported rotatably in a recess provided in said one end of the rocker arm, and transmits the up and down movement of the push rod to said one end of the rocker arm; and an adapter that is attached to said lash adjuster and interposed between said lash adjuster and said push rod, wherein an upper part of the adapter is attached to and integrated with the sliding part of the lash adjuster, and a lower part is supported by the upper end of the push rod, and the lash adjuster transmits the up and down movement of the push rod to the rocker arm via said adapter and adjusts valve clearance.

2. The valve train for an overhead valve engine as described in claim 1, characterized in that the adapter and the upper end of the push rod are supported by a joint connection in which one is configured as a convex portion and the other is configured as a concave portion, and the convex portion is rotatably inserted into the inside of the concave portion and supported, and the bottom surface of the adapter that abuts against the push rod is surface-treated to reduce wear with the push rod.

3. The valve train for an overhead valve engine according to claim 2, wherein a groove for retaining oil is formed on the bottom surface of the adapter.

4. A valve train for an overhead valve engine as set forth in any one of claims 1 to 3, characterized in that the mechanism is configured to be assembled by inserting the sliding portion into the concave engaging portion of the adapter, the sliding portion of the lash adjuster has an outer peripheral groove on the outer surface thereof and an inner peripheral groove on the inner surface thereof, and the adapter is fixed to the sliding portion by engaging members that fit into the outer peripheral groove and the inner peripheral groove.

Images