JP2007092630A - Lash adjuster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability and reliability of a lash adjuster by reducing stress acting on a diaphragm. <P>SOLUTION: A high pressure chamber 45 is formed by slidably fitting a plunger 42 in a body 41, and a reservoir chamber 56 is formed by energizing the plunger 42 in a projection direction by a plunger spring 50 and joining one end part of the diaphragm 51 to a body 41 and joining the other end thereof to the plunger 42. A communication passage 42c allowing movement of working fluid from the reservoir chamber 56 to the high pressure chamber 45 according to pressure in the high pressure chamber 45 is provided. The diaphragm 51 is installed in such a manner that the diaphragm 51 takes a natural shape on a roughly middle position of a movement stroke S of the plunger 42 to a body 41. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lash adjuster for adjusting a gap between components in a valve mechanism of an internal combustion engine.

  For example, in an internal combustion engine, the engine body becomes hot due to combustion in the combustion chamber, and the heat is transmitted to the valve mechanism so that the valve mechanism also becomes hot. In order to prevent this, a lash adjuster for adjusting the gaps (clearances) between the components in the valve operating mechanism is provided. This lash adjuster is interposed between components that are displaced during the operation of the valve mechanism, and prevents the formation of gaps following the change in the distance between them. Wear during operation can be reduced.

  As a conventional lash adjuster applied to an internal combustion engine, for example, there is one described in Patent Document 1 below. In the lash adjuster described in Patent Document 1, a plunger is slidably fitted to a body, and is urged and supported by an elastic member so that one end protrudes outward. A high-pressure chamber is formed by the recess, and a reservoir chamber is formed by attaching a diaphragm between the body and the plunger. The high-pressure chamber and the reservoir chamber communicate with each other through a communication path, and a check valve is provided. While allowing the flow from the reservoir chamber to the high pressure chamber, the flow from the high pressure chamber to the reservoir chamber is blocked.

  Therefore, when the plunger is pressed by the cam through the rocker arm, the pressure in the high pressure chamber is increased, the communication path is closed by the check valve, and when the plunger stops, the rocker arm rotates and the valve is pushed down. Open. When the rocker arm is not pressed by the cam, the valve starts to rise while the pressure in the high pressure chamber is maintained. When the valve is closed, the plunger moves by the resilient member to eliminate the valve clearance, and at the same time, the pressure from the reservoir chamber increases. The hydraulic fluid flows into the chamber and enters a standby state.

JP-A-62-023508

  By the way, in the lash adjuster described above, the plunger protrudes when absorbing the difference in thermal expansion between the intake / exhaust valve and the cylinder head, and the plunger is immersed to absorb wear of the valve operating mechanism. Therefore, in a state where this lash adjuster is mounted on the valve mechanism of the internal combustion engine, the plunger is at a position where it is stopped at an approximately middle position of its moving stroke. However, in the conventional lash adjuster described above, the plunger is biased and supported so as to protrude outward from the body, and is positioned at the maximum extension position by a retaining ring, and at this maximum extension position, the diaphragm is positioned. Are attached in a natural shape, that is, a vulcanized shape. Therefore, when the lash adjuster is mounted on the valve mechanism of the internal combustion engine, a stress is applied to the diaphragm, which causes cracks due to the constantly acting stress.

  In the lash adjuster, when the plunger is pressed and the full stroke is reached, the hydraulic oil in the high-pressure chamber moves to the reservoir chamber. In this reservoir chamber, the diaphragm expands and expands its volume to receive the hydraulic oil. Yes. At this time, since the hydraulic oil is accompanied by thermal expansion, the diaphragm needs to absorb thermal expansion of the hydraulic oil. However, in the conventional lash adjuster described above, the diaphragm is attached so as to form a natural shape at the most extended position where the plunger protrudes outward from the body. Therefore, during the plunger stroke, the diaphragm expands (expands), and there is a possibility that the original shape cannot be maintained due to the repeated expansion operation of the diaphragm, which also causes cracking.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide a lash adjuster in which the stress acting on the diaphragm is reduced to improve durability and reliability.

  In order to solve the above-described problems and achieve the object, the lash adjuster of the present invention includes a body having a bottomed cylindrical shape, a plunger that forms a high-pressure chamber by being slidably fitted to the body, A biasing member that biases the plunger in a direction protruding from the body, and a diaphragm that forms a reservoir chamber by forming a cylindrical shape, with one end joined to the body and the other end joined to the plunger. And a communication adjuster that allows movement of hydraulic oil from the reservoir chamber to the high pressure chamber according to the pressure of the high pressure chamber, wherein the diaphragm is formed by an elastic member, and the plunger for the body The diaphragm is mounted so as to have a natural shape at substantially the middle position of the moving stroke.

  The lash adjuster of the present invention is characterized in that the natural shape of the diaphragm is a molded shape in which no stress is applied from the outside.

  The lash adjuster of the present invention is characterized in that the diaphragm has a slack portion that can be extended in the natural shape.

  The lash adjuster according to the present invention is characterized in that the diaphragm is mounted so as to have a natural shape on the protruding side from an intermediate position of the movement stroke of the plunger with respect to the body.

  According to the lash adjuster of the present invention, a plunger is slidably fitted into a bottomed cylindrical body to form a high pressure chamber, and one end of a cylindrical diaphragm is joined to the body. A reservoir chamber is formed by joining the end to the plunger, and a communication path is provided that allows the hydraulic oil to move from the reservoir chamber to the high pressure chamber according to the pressure in the high pressure chamber. The diaphragm is formed by an elastic member. Since the diaphragm is mounted in a natural shape at approximately the middle position of the plunger movement stroke relative to the body, when the lash adjuster is mounted on the valve mechanism, the plunger is positioned at approximately the middle position of the movement stroke. In this state, the diaphragm is maintained in its natural shape so that no stress acts on it. Load expansion amount at the time of expansion and contraction decreases in diaphragm and also becomes to be reduced, thereby improving the durability and reliability by reducing the stress acting on the diaphragm.

  Embodiments of a lash adjuster according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a cross-sectional view of a lash adjuster according to an embodiment of the present invention, FIG. 2 is a cross-sectional view illustrating a state in which a diaphragm is attached to the lash adjuster of the present embodiment, and FIG. 3 is a top view of the lash adjuster of the present embodiment. FIG. 4 is a cross-sectional view showing the most sunk operation state of the lash adjuster of this embodiment, FIG. 5 is a cross-sectional view showing the expansion / contraction state of the diaphragm in the lash adjuster of this embodiment, and FIG. These are principal part sectional drawings of the engine to which the lash adjuster of the present Example was applied.

  In the engine to which the lash adjuster of this embodiment is applied, as shown in FIG. 6, a cylinder block 12 is assembled to the lower part of the cylinder head 11 and fastened by a plurality of fastening bolts (not shown). A plurality of cylinder bores 13 are formed in the cylinder block 12, and a piston 14 is slidably fitted to each cylinder bore 13. A crankshaft (not shown) is rotatably supported at the lower part of the cylinder block 12, and each piston 14 is connected to the crankshaft via a connecting rod 15.

  The combustion chamber 16 is constituted by a cylinder bore 13 formed in the cylinder block 12, a lower surface of the cylinder head 11, and a top surface of the piston 14, so that a central portion of the ceiling portion (lower surface of the cylinder head 11) is raised. It has a pent roof shape that is slanted. An intake port 17 and an exhaust port 18 are formed to face the upper portion of the combustion chamber 16, that is, the lower surface of the cylinder head 11, and the intake valve 19 and the exhaust valve are opposed to the intake port 17 and the exhaust port 18. 20 is located respectively. The intake valve 19 and the exhaust valve 20 are supported by the stem guides 21 and 22 fixed to the cylinder head 11 so as to be movable along the axial direction, and the intake ports 17 and the exhaust ports are supported by the valve springs 23 and 24. It is urged and supported in a direction to close 18. Further, the intake valve 19 and the exhaust valve 20 are connected to upper end portions of one end of roller rocker arms 25 and 26, and the other end portions of the roller rocker arms 25 and 26 are connected to lash adjusters 27 and 28 fixed to the cylinder head 11. The intake camshaft 29 has an intake cam 30 and the exhaust camshaft 31 has an exhaust cam 32 in contact with the roller rocker arms 25 and 26.

  Therefore, when the intake camshaft 29 and the exhaust camshaft 31 rotate in synchronization with the engine, the intake cam 30 and the exhaust cam 32 actuate the roller rocker arms 25 and 26, and the intake valves 19 and the exhaust valves 20 are moved at a predetermined timing. By moving up and down, the intake port 17 and the exhaust port 18 can be opened and closed, and the intake port 17 and the combustion chamber 16 can communicate with the combustion chamber 16 and the exhaust port 18, respectively.

  A fuel injection valve 33 that directly injects fuel into the combustion chamber 16 is mounted on the side of the combustion chamber 16, that is, on the lower surface of the cylinder head 11 on the intake port 17 side. A spark plug 34 is attached to the center of the ceiling of the combustion chamber 16, that is, the lower surface of the cylinder head 11 between each intake port 17 and each exhaust port 18. The vehicle is equipped with an electronic control unit (ECU), which can control the fuel injection timing of the fuel injection valve 33, the ignition timing by the spark plug 34, and the like. The fuel injection amount, the injection timing, the ignition timing, and the like are determined based on the engine operating state such as the throttle opening (accelerator opening) and the engine speed.

  In the valve operating mechanism including the intake valve 19 and the exhaust valve 20 described above, the lash adjusters 27 and 28 adjust the gaps between the constituent members of the valve operating mechanism. Absorbs wear during operation. In the following, the lash adjusters 27 and 28 of this embodiment will be described. Since both have substantially the same configuration, only the lash adjuster 27 provided on the intake valve 19 side will be described in detail.

  In the lash adjuster 27, as shown in FIGS. 1 and 2, the body 41 fixed to the cylinder head 11 has a bottomed cylindrical shape, and the outer peripheral portion of the upper end has a disk-shaped flange portion 41a that spreads outward. Is formed. The plunger 42 is slidably fitted into the body 41 on the base end side, and the position where the first stopper portion 42 a abuts on the step portion 41 b of the body 41 and the second stopper portion 42 b are attached to the body 41. It is possible to slide between the position abutting against the stopper ring 43. The plunger 42 has a communication passage 42c formed in the central portion along the axial direction. The upper end of the communication passage 42c is closed by the plug ball 44, while the lower end is connected to the bottom of the body 41 via the recess 42d. The high-pressure chamber 45 is formed here.

  A ring-shaped valve seat 46 is fixed to the concave portion 42d of the plunger 42. A check ball 47 as a check valve for opening and closing the communication passage 42c is supported on the valve seat 46 by a check ball gauge 48. The ball spring 49 urges the communication passage 42c to close. A plunger spring 50 as an urging member is interposed between the check ball gauge 48 and the bottom of the body 41, and urges the plunger 42 in a direction protruding from the body 41.

  The diaphragm 51 has a deformable cylindrical shape, and a lower end portion thereof is fitted in a step portion on the outer peripheral surface of the flange portion 41a of the body 41 along the vertical direction, and a ring-shaped holder 52 is attached from the outside thereof. Since 52 is fixed to the body 41 by a method such as caulking, the lower end portion of the diaphragm 51 is joined to the flange portion 41a. On the other hand, the plunger 42 is exposed to the outside from the body 41, and the tip of the plunger 42 has a spherical shape so that the end of the roller rocker arm 25 can be connected. A ring-shaped first cap 53 is press-fitted into the outer peripheral portion of the plunger 42, and the other end of the diaphragm 51 along the horizontal direction is fitted onto the first cap 53. A second cap 54 having a ring shape is press-fitted. A rubber rubber ring 55 is interposed between the other end of the diaphragm 51 and the second cap.

  That is, the first cap 53 is press-fitted into the outer peripheral portion of the plunger 42 and positioned and fixed by contacting the stepped portion 42e. The other end of the diaphragm 51 is formed thick, the inner peripheral surface thereof is fitted to the outer peripheral surface of the plunger 42 without a gap, and the lower surface is in close contact with the upper surface of the first cap 53. The rubber ring 55 has a predetermined thickness and is fitted to the outer peripheral portion of the plunger 42, and is slightly bent upward so that the lower surface is in close contact with the upper surface of the diaphragm 51 and the outer peripheral portion is separated from the plunger 42. is doing. The second cap 54 is press-fitted into the outer peripheral portion of the plunger 42, and the lower surface is in close contact with the upper surface of the rubber ring 55.

  Therefore, one end of the diaphragm 51 is joined to the flange portion 41 a of the body 41 by the holder 52, while the other end is sandwiched and joined by the two caps 53 and 54 and the rubber ring 55. A reservoir chamber 56 is formed in the diaphragm 51 and communicates with the communication path 42 c through a through hole 42 f formed in the plunger 42. In this case, the stopper ring 43 is attached above the upper surface of the flange portion 41a, so that the movement distance of the plunger 42 is sufficiently secured and the volume of the reservoir chamber 56 is sufficiently secured.

  A fluororesin (for example, tetrafluoroethylene resin-PTFE) 57 is vulcanized and bonded to the surface of the diaphragm 51 as a rigidity improving layer for increasing the rigidity. For this reason, the surface of the diaphragm 51 is hardened and deterioration due to the lubricating oil or blow-by gas is suppressed, and unnecessary deformation is suppressed.

  In the lash adjuster 27 of the present embodiment configured as described above, the diaphragm 51 is vulcanized and molded with rubber as an elastic member, and is at an approximately middle position of the movement stroke S of the plunger 42 with respect to the body 41. The diaphragm 51 is mounted so as to have a natural shape, that is, a molded shape in which no stress is applied from the outside.

  That is, the lash adjuster 27 needs to move in the direction in which the plunger 42 protrudes with respect to the body 41 when absorbing the thermal expansion difference between the intake / exhaust valves 19, 20 and the cylinder head 11. In order to absorb wear of the intake / exhaust valves 19 and 20 and the valve seat, the plunger 42 needs to move in a direction to be immersed in the body 41. Therefore, in a state in which the lash adjuster 27 is assembled to the valve mechanism of the internal combustion engine, the plunger 42 is positioned at an approximately middle position of the movement stroke, and can be moved in either the protruding side or the immersive side. ing. In the present embodiment, the lash adjuster 27 is attached to the valve mechanism so that the diaphragm 51 is in a natural shape.

  Therefore, the diaphragm 51 has the above-described natural shape, the vertical wall portion 51a extending upward from the outer peripheral portion of the flange portion 41a of the body 41, and the horizontal wall portion 51b extending outward from the outer peripheral portion of the plunger 42. And a slack portion 51c that connects the vertical wall portion 51a and the horizontal wall portion 51b. Therefore, at the most extended position of the lash adjuster 27 where the plunger 42 protrudes from the body 41, the hydraulic oil in the reservoir chamber 56 flows into the pressure chamber 45 as shown by the solid line in FIGS. When the vertical wall portion 51a is pulled inward and the horizontal wall portion 51b is pulled upward, the slack portion 51 is deformed and the volume change (reduction) of the reservoir chamber 56 can be absorbed. On the other hand, since the hydraulic oil in the pressure chamber 45 flows into the reservoir chamber 56 as shown by a two-dot chain line in the lash adjuster 27 in which the plunger 42 is pushed into the body 41, as shown in FIGS. 51, the vertical wall portion 51a, the horizontal wall portion 51b, and the slack portion 51c are deformed outward to absorb the volume change (enlargement) of the reservoir chamber 56.

  In the above description, the diaphragm 51 is mounted so as to have a natural shape at a substantially intermediate position of the movement stroke S of the plunger 42 with respect to the body 41. However, the stopper portions 42a and 42b of the plunger 42 are stepped portions of the body 41. The diaphragm 51 may be mounted so as to have a natural shape at a predetermined position between the most extended position and the most depressed position of the lash adjuster 27 before contacting the 41b and the stopper ring 43. In this case, it is desirable that the diaphragm 51 is mounted so as to have a natural shape slightly on the maximum extension position side from the intermediate position of the movement stroke S of the plunger 42 relative to the body 41. In consideration of the life of the lash adjuster 27, the stroke due to wear of the intake / exhaust valves 19, 20 and the valve seat is more than the stroke change due to the difference in thermal expansion between the intake / exhaust valves 19, 20 and the cylinder head 11. Since the amount of change increases, it is preferable that the plunger 42 be mounted so as to have a natural shape at a position where the plunger 42 has secured a larger movement stroke toward the most depressed position than a movement stroke toward the most extended position.

  Here, the operation of the lash adjuster 27 of the present embodiment will be described. The lash adjuster 27 shown in FIG. 3 is located at the maximum extension position where the plunger 42 is located at the highest point, and when the plunger 42 is assembled to the valve operating mechanism, as shown in FIG. The state is lowered by S / 2. In the assembled state of the lash adjuster 27, since the diaphragm 51 has a natural shape, unnecessary stress is not applied from the outside.

  From this assembled state, as shown in FIGS. 1 and 6, the camshaft 29 rotates and the intake cam 30 presses the roller rocker arm 25, and a load acts on both the intake valve 19 and the plunger 42 of the lash adjuster 27. To do. Then, the plunger 42 of the lash adjuster 27 begins to descend into the body 41 against the urging force of the plunger spring 50, the hydraulic oil in the high pressure chamber 45 is pressurized to a pressure higher than the reservoir chamber 56, and the check ball 47 is The communication path 42c is closed.

  When the communication path 42c is closed, the flow of hydraulic oil from the high pressure chamber 45 to the reservoir chamber 56 through the communication path 42c is stopped, and the lowering of the plunger 42 is also stopped. Therefore, the roller rocker arm 25 swings with the upper end of the plunger 42 as a fulcrum, and pushes down the intake valve 19 to open the intake port 17. During this operation, the plunger 42 receives a downward force by the roller rocker arm 25, and the hydraulic oil in the high pressure chamber 45 gradually returns to the reservoir chamber 56 through the sliding portion between the body 41 and the plunger 42. As shown in FIG. 4, the plunger 42 is displaced downward, and the lash adjuster 27 gradually contracts.

  At this time, the diaphragm 51 absorbs the volume change by expanding so as to be displaced outward as the volume of the reservoir chamber 56 increases. And when this diaphragm 51 expand | swells, an outer surface contacts the rubber ring 55, and a contact with the 2nd cap 54 is prevented and a crack and damage are prevented without being rubbed. Note that a fluororesin is vulcanized and bonded to the surface of the diaphragm 51. Generally, the fluororesin has a characteristic of being easily worn out by a metal, but in this embodiment, the contact with the second cap 54 is caused by a bent structure. Since it is prevented, the effect of preventing cracks and damage to the fluororesin and the diaphragm 51 can be improved.

  Thereafter, as shown in FIGS. 4 and 6, when the intake cam 30 passes the maximum lift, the roller rocker arm 25 swings in the direction opposite to that described above while the pressurized state of the high pressure chamber 45 is maintained, and the intake valve 19. Is raised by the urging force of the valve spring 23 to close the intake port 17. Then, the pressing of the lash adjuster 27 to the plunger 42 by the roller rocker arm 25 is finished, the plunger 42 is raised by the urging force of the plunger spring 50, and the high pressure chamber 45 is released from the pressurized state. Then, the check ball 47 stops closing the communication path 42c and allows the hydraulic oil to flow from the reservoir chamber 56 to the high-pressure chamber 45. As shown in FIG. By flowing into the chamber 45, the volume of the reservoir chamber 56 is reduced, and the diaphragm 51 contracts to the original state, that is, the natural shape.

  At this time, the diaphragm 51 absorbs the volume change by contracting so as to be displaced inward as the volume of the reservoir chamber 56 decreases. The diaphragm 51 is displaced so as to bend toward the first cap 53, and the inner surface approaches the outer peripheral corner of the first cap 53. Since a gap is provided here, the inner surface of the diaphragm 51 is There is no direct contact between the first cap 53 and the diaphragm 51, so that cracking and damage to the diaphragm 51 can be prevented and stress concentration can be avoided.

  Further, when a thermal expansion difference occurs between the intake / exhaust valves 19, 20 and the cylinder head 11, the lash adjuster 27 moves in a direction in which the plunger 42 protrudes with respect to the body 41 and absorbs this thermal expansion difference. When wear occurs in the valve operating mechanism, the plunger 42 moves into the body 41 so as to be absorbed, and this wear is absorbed.

  Although only the intake-side lash adjuster 27 has been described here, the exhaust-side lash adjuster 28 has the same configuration and exhibits the same functions and effects.

  As described above, in the lash adjusters 27 and 28 of the present embodiment, the plunger 42 is slidably fitted to the body 41 to form the high-pressure chamber 45, and the plunger 42 is moved outward by the plunger spring 50. Energizing in the protruding direction, one end of the diaphragm 51 is joined to the body 41 while the other end is joined to the plunger 42 to form a reservoir chamber 56, and the reservoir chamber 56 is formed according to the pressure in the high-pressure chamber 45. A communication passage 42c that allows the movement of hydraulic oil from the high pressure chamber 45 to the high pressure chamber 45 is provided, and the diaphragm 51 is mounted so as to have a natural shape at a substantially intermediate position of the movement stroke S of the plunger 42 relative to the body 41.

  Accordingly, in a state where the lash adjusters 27 and 28 are mounted on the valve operating mechanism, the plunger 42 is stopped at a substantially intermediate position of the moving stroke S with respect to the body 41, and in this state, the diaphragm 51 is maintained in a natural shape. Therefore, it can be maintained in a free state where no external stress is applied. Further, by reducing the amount of movement of the plunger 42 from the intermediate position to the most extended position or the most depressed position, the expansion / contraction amount of the diaphragm 51 associated therewith can be reduced, and the load on the diaphragm 51 during expansion / contraction can be reduced. . As a result, the stress acting on the diaphragm 51 can be reduced and the durability and reliability can be improved.

  Further, in the lash adjusters 27 and 28 of the present embodiment, the diaphragm 51 is mounted so as to have a natural shape at a substantially intermediate position of the movement stroke S of the plunger 42 with respect to the body 41. In the most extended state protruding, the volume of the reservoir chamber 56 is reduced. Therefore, the filling amount of the hydraulic oil sealed before assembly can be reduced, and the manufacturing cost can be reduced.

  As described above, the lash adjuster according to the present invention is designed to improve the durability and reliability by reducing the stress acting on the diaphragm constituting the reservoir chamber. It is also useful to apply.

It is sectional drawing of the lash adjuster which concerns on one Example of this invention. It is sectional drawing showing the attachment state of the diaphragm in the lash adjuster of a present Example. It is sectional drawing showing the maximum extension operation state of the lash adjuster of a present Example. It is sectional drawing showing the most subsidence operation state of the lash adjuster of a present Example. It is sectional drawing showing the expansion-contraction state of the diaphragm in the lash adjuster of a present Example. It is principal part sectional drawing of the engine to which the lash adjuster of a present Example was applied.

Explanation of symbols

19 Intake valve 20 Exhaust valve 23, 24 Valve spring 25, 26 Roller rocker arm 27, 28 Rush adjuster 29 Intake camshaft 30 Intake cam 31 Exhaust camshaft 32 Exhaust cam 41 Body 42 Plunger 42c Communication path 45 High pressure chamber 47 Check ball 50 Plunger Spring (biasing member)
51 Diaphragm 51c Slack part 56 Reservoir chamber

Claims (4)

  A body having a bottomed cylindrical shape, a plunger that is slidably fitted to the body to form a high-pressure chamber, a biasing member that biases the plunger in a direction protruding from the body, and a cylindrical shape A diaphragm having one end joined to the body and the other end joined to the plunger to form a reservoir chamber, and hydraulic oil from the reservoir chamber to the high pressure chamber according to the pressure of the high pressure chamber In a lash adjuster having a communication passage that allows movement of the diaphragm, the diaphragm is formed by an elastic member, and is mounted so that the diaphragm has a natural shape at a substantially intermediate position of the movement stroke of the plunger with respect to the body. Rush adjuster characterized by.   2. The lash adjuster according to claim 1, wherein the natural shape of the diaphragm is a molded shape in which no stress is applied from the outside.   3. The lash adjuster according to claim 1, wherein the diaphragm includes a slack portion that is stretchable in the natural shape. 4. 2. The lash adjuster according to claim 1, wherein the diaphragm is mounted so as to have a natural shape on a protruding side from an intermediate position of a movement stroke of the plunger with respect to the body. 3.

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