JP7264757B2 - valve train - Google Patents

Description

The present invention relates to valve trains.

A valve train disclosed in Patent Document 1 includes a tappet for an internal combustion engine such as an automobile engine. This tappet includes a lash adjuster and a tappet body into which the lash adjuster is inserted.

In the valve train described above, when the cam rotates, the tappet body in contact with the cam slides vertically in the tappet guide hole, and the push rod is moved up and down via the lash adjuster. The valve clearance is automatically adjusted by transmitting the lift force of the cam through the lash adjuster to the push rod and the rocker arm after being attenuated.

WO2018/147092

In the configuration disclosed in Patent Document 1, the lash adjuster is incorporated in the tappet body. With such a configuration, the outer diameter of the tappet must be large enough to incorporate the lash adjuster, and depending on the inner diameter of the tappet bore, the tappet may not be able to be inserted into the tappet bore.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a valve train capable of automatically adjusting the valve clearance regardless of the inner diameter of the tappet bore. .

A valve train according to the present invention includes a valve, a rocker arm that swings around a rocker shaft to open and close the valve arranged at one end, and a push arm that transmits power to the other end of the rocker arm. a rod, a tappet that reciprocates while being in sliding contact with the inner peripheral surface of the tappet bore according to the rotation of the cam to transmit power to the push rod, and a hydraulic lash adjuster that adjusts the valve clearance. . The lash adjuster has a bottomed cylindrical body and a plunger reciprocatingly inserted into the body. In the body, a high-pressure chamber is formed which is partitioned from the low-pressure chamber by the bottom wall of the plunger and filled with the hydraulic oil. A valve hole is provided through the high-pressure chamber to communicate between them, and a valve element for opening and closing the valve hole is provided in the high-pressure chamber. The push rod is provided with a support for supporting the body, and the support is arranged outside the tappet bore.

According to this valve train, the existing lash adjuster can be arranged outside the tappet bore by supporting the body with the support portion of the push rod. As a result, it is possible to provide a valve train in which the valve clearance can be adjusted regardless of the inner diameter of the tappet bore.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure showing the valve gear which concerns on Example 1 of this invention. It is a figure which expands and shows the lash adjuster and support part of FIG.

Preferred embodiments of the present invention are shown below.
The support portion may be provided at the upper end of the push rod, and the plunger of the lash adjuster may contact the rocker arm while the body is supported by the support portion. According to this configuration, the push rod, the lash adjuster, and the rocker arm can be assembled together with a simple configuration.

The support portion may be recessed downward and have a recess into which the body can be inserted, and the upper end of the recess may be located above the upper end of the peripheral wall of the body. According to this configuration, since the hydraulic oil can be stored in the recessed portion, it is possible to suppress the hydraulic oil from flowing out of the lash adjuster.

The push rod may have an air vent hole that opens to the inner surface of the recess and discharges air existing between the support portion and the body to the outside. This configuration makes it easier to insert the lash adjuster into the recess.

The air vent hole may open in the bottom surface of the recess. According to this configuration, since a clearance is unlikely to occur between the bottom surface of the recess and the lash adjuster, the lash adjuster can be brought into contact with the bottom surface of the recess and the opening of the air vent hole can be closed by the lash adjuster. As a result, it is possible to suppress the hydraulic oil from flowing out from the air vent hole.

The air vent hole may axially pass through the push rod. According to this configuration, during use, the tappet can close the opening on the lower end side of the air vent hole, and foreign matter can be prevented from entering the air vent hole.

<Example 1>
Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. A valve train 10 according to the first embodiment constitutes a valve lifter for an OHV (Over Head Valve) type engine.

The valve train 10 includes a valve 20, a rocker arm 30, a push rod 40, a tappet 50, and a lash adjuster 60, as shown in FIG. The valve train 10 includes a valve 20 that can open and close an intake or exhaust port 92 of a cylinder head 91 , and a tappet 50 that can reciprocate within a tappet bore 95 of a cylinder block (housing) 94 . The tappet bore 95 has a circular cross-section and is provided so as to pass through a predetermined portion of the cylinder block 94 .

The valve 20 is arranged such that its upper end projects upward from the cylinder head 91 . The valve 20 is vertically slidably inserted into the valve guide hole 93 and is biased in the valve closing direction (the direction in which the one end 31 of the rocker arm 30 is lifted) by a biasing member 21 such as a coil spring.

The rocker arm 30 is configured to extend longitudinally from one end 31 to the other end 32 . The rocker arm 30 is a member that swings around a rocker shaft 96 to open and close the valve 20 arranged on the one end 31 side. One end 31 of the rocker arm 30 contacts the upper end of the valve 20 . The rocker shaft 96 penetrates the rocker arm 30 through the lengthwise intermediate portion (the portion between the one end portion 31 and the other end portion 32). The rocker arm 30 has an adjusting screw 33 at the other end 32 . The adjusting screw 33 passes through the other end 32 of the rocker arm 30 and is screwed into the nut 34 so that the amount of downward projection from the other end 32 of the rocker arm 30 can be adjusted in accordance with the screwing into the nut 34 . ing. A downwardly opening hemispherical support recess 35 is provided at the lower end of the adjusting screw 33 . A lash adjuster 60 is held between the bearing recess 35 and the push rod 40 . A configuration related to the push rod 40 will be described later.

The tappet 50 is a member that is reciprocatingly displaced while being in sliding contact with the inner peripheral surface of the tappet bore 95 according to the rotation of the cam 97 to transmit power to the push rod 40 . The tappet 50 has a substantially cylindrical main body portion 51 inserted into the tappet bore 95 and a brim-shaped flange portion 52 provided at the lower end portion of the main body portion 51 . The inner diameter of the tappet bore 95 may be restricted by the size and layout of the engine due to the structure provided in the cylinder block 94 . In this embodiment, since the tappet 50 has a simple configuration, it is suitable for an engine having a tappet bore 95 with a smaller inner diameter than, for example, a configuration in which a lash adjuster is provided on the tappet. A lower surface of the tappet 50 serves as a cam slide contact surface 53 with which the cam 97 slides. The upper surface of the tappet 50 is provided with a bearing recess 54 having a radius of curvature larger than the lower end 42 (convex spherical surface) of the pushrod 40, which will be described later.

The lash adjuster 60 is a hydraulic lash adjuster that adjusts valve clearance. The lash adjuster 60 has a bottomed tubular body 71 and a bottomed tubular plunger 81 inserted into the body 71 so as to be vertically movable. The body 71 has a circular bottom wall 72 and a cylindrical peripheral wall 73 rising from the peripheral edge of the bottom wall 72 . A body oil hole 74 is provided through a peripheral wall 73 of the body 71 . The plunger 81 has a circular bottom wall 82 , a cylindrical peripheral wall 83 rising from the peripheral edge of the bottom wall 82 , and a hemispherical top 85 provided at the upper end of the peripheral wall 83 . A plunger oil hole 84 is provided through a peripheral wall 83 of the plunger 81 . The radius of curvature of the outer peripheral surface (convex spherical surface) of the top portion 85 is smaller than the radius of curvature of the inner peripheral surface (concave spherical surface) of the bearing recess 35 . A top hole 86 is provided through the center of the top portion 85 .

A low-pressure chamber 61 in which hydraulic oil is stored is provided in the plunger 81 . A high-pressure chamber 62 partitioned from a low-pressure chamber 61 by a bottom wall 82 of the plunger 81 is formed in the body 71 . A bottom wall 82 of the plunger 81 is provided with a valve hole 63 penetrating therethrough for communicating between the low pressure chamber 61 and the high pressure chamber 62 . Hydraulic oil is introduced into the low-pressure chamber 61 through the top hole 86 and stored therein. The high-pressure chamber 62 is filled with hydraulic fluid from the low-pressure chamber 61 through the valve hole 63 . In the following description, when hydraulic oil plays a lubricating role in the valve train 10, it is also referred to as lubricating oil.

The body oil hole 74 of the lash adjuster 60 communicates with the low pressure chamber 61 inside the plunger 81 via the plunger oil hole 84 . The body oil hole 74 and the plunger oil hole 84 are communicated with an oil gallery of the cylinder head when the lash adjuster 60 is assembled to the cylinder head and used in an OHC (Over Head Camshaft) engine so that low pressure can be drawn from the oil gallery. It was necessary to allow the hydraulic oil to flow into the chamber 61 . In the case of this embodiment, since the existing lash adjuster 60 is used, the body oil hole 74 and the plunger oil hole 84 are formed in the lash adjuster 60 .

The high-pressure chamber 62 accommodates a spherical valve body 64 , a cage-like retainer 65 , a first spring 66 and a second spring 67 . The valve body 64 is housed in a retainer 65 and arranged to open and close the valve hole 63 . The first spring 66 is accommodated in the retainer 65 and biases the valve body 64 upward (to close the valve hole 63). Also, the second spring 67 urges the retainer 65 upward. In addition, in the case of the first embodiment, the existing (general-purpose) lash adjuster 60 is used as it is.

The push rod 40 is a member that transmits power to the other end 32 side of the rocker arm 30 . The push rod 40 includes a rod-shaped rod portion 41 elongated in the vertical direction, and a support portion 45 that supports the body 71 of the lash adjuster 60 . A lower end 42 of the rod portion 41 is formed in a convex spherical shape, and serves as a pressure receiving surface that abuts against the tappet 50 and receives a load. The support portion 45 is provided on the upper end side of the rod portion 41 and has a cup shape that is larger in diameter than the rod portion 41 and coaxial with the rod portion 41 . The push rod 40 has, between the support portion 45 and the rod portion 41, a reduced diameter portion 43 whose outer diameter decreases downward from the support portion 45. As shown in FIG. The outer peripheral surface of the reduced diameter portion 43 forms an inclined surface that is inclined with respect to the axial direction of the push rod 40 .

The support 45 is arranged outside the tappet bore 95 . In this embodiment, the support 45 has an outer diameter greater than the inner diameter of the tappet bore 95 . This support portion 45 is a structure for installing the existing lash adjuster 60 outside the tappet bore 95 in an engine having a tappet bore 95 with a small inner diameter. The support portion 45 is provided at the upper end of the push rod 40 . In the lash adjuster 60 , the plunger 81 contacts the rocker arm 30 while the body 71 is supported by the support portion 45 . Specifically, the top portion 85 of the plunger 81 slidably contacts the inner peripheral surface of the support recess 35 of the rocker arm 30 . In this state, the oil passage 36 of the rocker arm 30 opening in the bearing recess 35 communicates with the top hole 86 of the plunger 81 .

The support portion 45 is recessed downward and has a recess 46 into which the body 71 can be inserted. The recessed portion 46 has a bottom surface 47 on which the bottom wall 72 of the body 71 is placed in contact, and side surfaces 48 surrounding the peripheral wall 73 of the body 71 with a clearance therebetween. A side surface 48 of the support portion 45 is arranged so as to be able to contact the outer peripheral surface of the body 71 . As a result, the lash adjuster 60 is held in a state where radial movement is restricted with respect to the support portion 45 . The upper end of the recess 46 (which is also the upper end of the support portion 45 and the push rod 40 ) is located above the upper end of the peripheral wall 73 of the body 71 . The upper end of the recess 46 is arranged at a position where it does not interfere with the support recess 35 while the plunger 81 is in contact with the support recess 35 . In the recess 46 , the space above the body oil hole 74 serves as a storage space 49 for storing therein hydraulic oil that flows out from the body oil hole 74 . Specifically, the body 71 is provided with an annular projection 75 above the body oil hole 74 . The ridge portion 75 is a structure for sealing the periphery of the body oil hole 74 and the oil gallery when the body oil hole 74 communicates with the oil gallery of the cylinder head or the like. In this embodiment, the storage space 49 is a space formed between the outer peripheral surface of the lash adjuster 60 and the inner peripheral surface of the recess 46 above the ridge portion 75 . With such a configuration, even when the internal combustion engine is stopped, the hydraulic oil level in the low-pressure chamber 61 of the lash adjuster 60 can be set to the height of the upper end of the recess 46 .

The push rod 40 has an air vent hole 44 that opens in the bottom surface 47 of the recess 46 and discharges air existing between the support portion 45 and the body 71 to the outside. When the bottom wall 72 of the body 71 is in contact with the bottom surface 47 , the bottom wall 72 closes the air vent hole 44 . The air vent hole 44 axially penetrates the push rod 40 . Specifically, the air vent hole 44 extends vertically through the support portion 45 , constitutes a hollow portion of the rod portion 41 , and is open to the outside at the lower end 42 of the push rod 40 .

Next, the procedure for assembling the lash adjuster 60 and the push rod 40 will be described.
First, the lash adjuster 60 is inserted into the support portion 45 of the push rod 40 . At this time, the air in the recessed portion 46 is released from the air vent hole 44 so that the lash adjuster 60 can be smoothly inserted into the recessed portion 46 . When the lash adjuster 60 is inserted into the recess 46 , the upper end opening of the air vent hole 44 is closed by the bottom wall 72 of the body 71 . The lower end 42 of the pushrod 40 then rests on the bearing recess 54 of the tappet 50 . Then, the tappet 50 closes the lower end opening of the air vent hole 44 . Furthermore, when each part of the valve train 10 is assembled, the lash adjuster 60 is held between the rocker arm 30 and the push rod 40 .

Next, the lubricating path along which lubricating oil reaches from the rocker arm 30 side to the cam 97 side will be described.
The lubricating oil flowing through the oil passage 36 of the rocker arm 30 moves to the other end 32 of the rocker arm 30 and flows into the lash adjuster 60 from the top hole 86 of the plunger 81 via the adjusting screw 33 . A portion of the lubricating oil that has flowed into the lash adjuster 60 flows out into the recess 46 via the plunger oil hole 84 and the body oil hole 74 and is stored in the storage space 49 of the recess 46 . Lubricating oil may directly drop from the outer surface of the top portion 85 and flow into the storage space 49 of the concave portion 46 without passing through the inside of the lash adjuster 60 . In this embodiment, since the upper end of the recess 46 is located above the upper end of the peripheral wall 73 of the body 71, the hydraulic oil stored in the low pressure chamber 61 is prevented from flowing out through the plunger oil hole 84 and the body oil hole 74. can be suppressed.

The lubricating oil that has flowed in exceeding the amount of storage in the storage space 49 of the recess 46 overflows the upper end of the recess 46 and flows downward along the outer surface of the support portion 45 . This lubricating oil reaches the lower end 42 of the rod portion 41 from the outer surface of the support portion 45 through the inclined surface of the reduced diameter portion 43 and the outer surface of the rod portion 41 . The lubricating oil reaching the lower end 42 of the rod portion 41 moves from the push rod 40 to the tappet 50 side to lubricate the tappet 50, the tappet bore 95 and the sliding area. Furthermore, the lubricating oil that has flowed into the bottom surface of the tappet 50 lubricates the sliding area between the tappet 50 and the cam 97 .

Next, the operating mode of the valve train 10 will be described. When the cam 97 rotates, the tappet 50 in contact with the cam 97 is vertically slidably displaced within the tappet bore 95, and the push rod 40 is moved up and down. The lifting motion of the push rod 40 is transmitted to the adjusting screw 33 of the rocker arm 30 via the lash adjuster 60 . As a result, the rocker arm 30 swings and one end 31 of the rocker arm 30 moves up and down, so that the valve 20 is opened and closed.

Here, when the plunger 81 is strongly pressed downward from the rocker arm 30 side as the push rod 40 rises, the valve body 64 closes the valve hole 63, the plunger 81 and the body 71 become rigid, and the plunger 81 descends. is regulated. When the pressure acting on the plunger 81 decreases as the push rod 40 descends, the second spring 67 pushes up the plunger 81 to increase the volume of the high pressure chamber 62 and reduce the pressure in the high pressure chamber 62 . As a result, the force that urges the valve body 64 in the valve closing direction is reduced, the valve body 64 opens the valve hole 63 , and the hydraulic fluid in the low pressure chamber 61 moves to the high pressure chamber 62 . In this manner, the lift force of the cam 97 is attenuated and transmitted to the rocker arm 30 via the lash adjuster 60, thereby automatically adjusting the valve clearance.

According to the valve train 10 of the first embodiment, the existing lash adjuster 60 can be arranged outside the tappet bore 95 by supporting the body 71 with the support portion 45 of the push rod 40 . As a result, it is possible to provide the valve operating system 10 capable of adjusting the valve clearance regardless of the inner diameter of the tappet bore 95 . Specifically, by disposing the support portion 45 of the lash adjuster 60 outside the tappet bore 95 , the existing lash adjuster 60 can be incorporated into the valve train 10 without increasing the diameter of the tappet bore 95 . Furthermore, by providing such a support portion 45 to the push rod 40, only the push rod 40 is newly installed, and the valve gear 10 can be constructed by using the existing parts for other parts constituting the valve gear 10. Can be configured. Another configuration for incorporating a lash adjuster in an engine having a small diameter tappet bore is to reduce the diameter of the lash adjuster according to the diameter of the tappet bore. However, the lash adjuster is composed of a large number of parts, and is a member that requires reliable operation, making it difficult to reduce the size of the lash adjuster. On the other hand, in this embodiment, since the support portion 45 is provided on the push rod 40, the existing lash adjuster 60 can be used, which is advantageous in terms of operational reliability and cost. Further, the push rod 40 having the support portion 45 can be used for various engines by changing the length of the rod portion 41, and has high versatility. Further, when the air vent hole 44 passes through the push rod 40 in the axial direction, forming the push rod 40 using a hollow member makes it possible to omit the process of processing the air vent hole separately. It can contribute to man-hour reduction.

<Other Examples>
Another embodiment will be briefly described below.
(1) The support portion may be provided at the lower end of the push rod. In this case, the top of the plunger of the lash adjuster may slidably abut the bearing recess of the tappet.
(2) The upper end of the recess need not be positioned above the upper end of the peripheral wall of the body. For example, even if the upper end of the recess is positioned above the body oil hole, the effect of suppressing the hydraulic oil stored in the low pressure chamber from flowing out to the outside through the plunger oil hole and the body oil hole to some extent. can be expected. Further, the supporting portion need not have a recess into which the body can be inserted, as long as the supporting portion can support the body.
(3) The air vent hole may open on the inner surface of the recess, for example, it may open on the side surface of the recess. Also, the air vent hole may penetrate the push rod in a direction intersecting the axial direction. With such a configuration, the length of the air vent hole can be shortened, and for example, when the air vent hole is formed in the push rod by post-processing, workability is excellent.
(4) The shape of the push rod can be changed as appropriate. For example, the push rod does not have a reduced diameter portion, and the outer peripheral surface of the support portion and the outer peripheral surface of the rod portion may be continuous with a step.
(5) The configuration of the lash adjuster can be changed as appropriate. For example, the lash adjuster may not have body oil holes and plunger oil holes.

DESCRIPTION OF SYMBOLS 10... Valve gear, 20... Valve, 30... Rocker arm, 31... One end part, 32... Other end part, 40... Push rod, 44... Air vent hole, 45... Support part, 46... Recessed part, 47... Bottom surface, 50 Tappet 60 Lash adjuster 61 Low pressure chamber 62 High pressure chamber 63 Valve hole 64 Valve body 71 Body 73 Peripheral wall 74 Body oil hole 81 Plunger 82 Bottom wall , 83... Peripheral wall, 84... Plunger oil hole, 95... Tappet bore, 96... Rocker shaft, 97... Cam

Claims (3)

a valve;
a rocker arm that swings around a rocker shaft to open and close the valve arranged at one end;
a push rod that transmits power to the other end of the rocker arm;
a tappet that is reciprocally displaced in the vertical direction while being in sliding contact with the inner peripheral surface of the tappet bore according to the rotation of the cam to transmit power to the push rod;
Equipped with a hydraulic lash adjuster that adjusts the valve clearance,
The lash adjuster has a cylindrical body with a bottom, and a plunger inserted into the body so as to reciprocate,
A low-pressure chamber in which hydraulic oil is stored is provided in the plunger,
A high-pressure chamber partitioned from the low-pressure chamber by a bottom wall of the plunger and filled with the hydraulic oil is formed in the body,
The bottom wall of the plunger is provided with a valve hole penetrating therethrough for communicating between the low-pressure chamber and the high-pressure chamber,
A valve element for opening and closing the valve hole is provided in the high-pressure chamber,
The push rod is integrally provided with a support for supporting the body,
The support portion is arranged outside the tappet bore , and has a concave portion at the upper end of the push rod that is concave downward and into which the body can be inserted,
The recess has a bottom surface on which the bottom wall of the body is placed in contact, and a side surface surrounding the peripheral wall of the body,
the plunger of the lash adjuster is in contact with the rocker arm in a state in which the body is supported by the support portion;
A valve gear in which an air vent hole for discharging air existing between the support portion and the body is open in the bottom surface of the recess. 2. The valve train according to claim 1 , wherein the upper end of said recess in said support portion is located above the upper end of said peripheral wall of said body . 3. A valve train according to claim 1 , wherein said air vent hole axially penetrates said push rod .

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