JP2007192111A - Hydraulic lash adjuster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic lash adjuster stably operating at either of low rotation speed or high rotation speed of an internal combustion engine. <P>SOLUTION: The hydraulic lash adjuster 30 is provided with a body 31 defining a high pressure chamber 37 and a low pressure chamber 38 and including an opening continuing to the low pressure chamber 37, a plunger 36 fitted in an opening of the body 31 and touching an rocker arm, and a plunger spring 32 and a check ball spring 34 generating force to promote push up of the plunger 36 toward the rocker arm by expansion and contraction. The plunger spring 32 and the check ball spring 34 is constructed with including shape memory alloy and are formed in such a manner that the same are relatively long at a time of low temperature and relatively short at a time of high temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic lash adjuster, and more particularly to a hydraulic lash adjuster having a telescopic member that pushes a plunger toward another member.

2. Description of the Related Art A hydraulic lash adjuster applied to a valve train of an internal combustion engine is conventionally known.
For example, Japanese Patent Application Laid-Open No. 5-156908 (Patent Document 1) discloses a structure intended to increase the inclination use limit angle of a lash adjuster of a valve mechanism of an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2004-197671 (Patent Document 2) discloses a structure intended to prevent a decrease in hardness of a portion constituting a lower end portion of a plunger and leakage of hydraulic oil in a low-pressure chamber.

In Japanese Patent Laid-Open No. 61-286509 (Patent Document 3), in a predetermined low temperature oil state, the check valve is contracted to open, and in a predetermined high temperature oil state, the check valve is urged in the valve closing direction. A hydraulic tappet is disclosed in which a spring made of a shape memory alloy that extends as much as possible is provided. Similarly, Japanese Utility Model Laid-Open No. 61-103509 (Patent Document 4) is characterized in that the check ball spring is made of a shape memory alloy whose force to push the check ball increases as the temperature rises. A hydraulic valve lifter is disclosed. Furthermore, Japanese Society of Invention and Innovation Technical Bulletin No. 2004-501590 (Non-Patent Document 1) also discloses a structure intended to increase the load of the check ball spring at a high temperature.
JP-A-5-156908 JP 2004-197671 A Japanese Patent Laid-Open No. 61-286509 Japanese Utility Model Publication No. 61-103509 Japan Society for Invention and Innovation Open Technical Bulletin No. 2004-501590

  When the internal combustion engine is running at a low speed, the oil in the lash adjuster is at a low temperature and the viscosity of the oil is relatively high. For this reason, the closing of the check ball tends to be delayed. Therefore, there is a demand for increasing the plunger push-up force by the return spring when the internal combustion engine rotates at a low speed. On the other hand, when the internal combustion engine is rotating at a high speed, a phenomenon in which the lash adjuster extends excessively (hereinafter sometimes referred to as “pump-up”) occurs, and the engine valve cannot be completely closed (hereinafter referred to as “unsteady”). May be referred to as a fully closed state). Therefore, there is a demand for weakening the plunger pushing-up force by the return spring at the time of high rotation of the internal combustion engine.

  On the other hand, Patent Documents 1 and 2 do not disclose the idea of making a difference in the pushing-up force of the plunger when the internal combustion engine is rotating at a low speed and at a high speed. Further, the configurations disclosed in Patent Literatures 3 and 4 and Non-Patent Literature 1 are configurations that are weak at the time of low rotation and generate a strong biasing force at the time of high rotation, and thus cannot satisfy the above-described requirements.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic lash adjuster that operates stably at both low and high speeds of an internal combustion engine. There is.

  The hydraulic lash adjuster according to the present invention defines a high-pressure chamber and a low-pressure chamber, a housing having an opening connected to the low-pressure chamber, a plunger fitted into the opening and in contact with another member, and by extending and contracting, And an expansion / contraction member that generates a force that promotes push-up toward another member, and the expansion / contraction member is relatively long at a low temperature and relatively short at a high temperature.

  According to the above configuration, the plunger push-up force can be increased at low temperatures, while the plunger push-up force can be reduced at high temperatures. As a result, a hydraulic lash adjuster that operates stably at both low and high speeds of the internal combustion engine can be obtained.

  In the hydraulic lash adjuster described above, the “force that promotes the pushing of the plunger toward another member” is indirectly determined by biasing the plunger directly and biasing a member other than the plunger. Power to promote the push-up of

  In the hydraulic lash adjuster, preferably, the elastic member is a spring including a shape memory alloy.

Thereby, the above-described effects can be obtained with a simple structure.
The hydraulic lash adjuster preferably further includes a partition portion that partitions the high pressure chamber and the low pressure chamber, and the spring biases the partition portion toward another member.

  According to the said structure, the force which a spring pushes up a plunger can be strong at the time of low rotation, and can be weakened at the time of high rotation. As a result, the pushing up of the plunger can be promoted at a low rotation and suppressed at a high rotation.

  The hydraulic lash adjuster is preferably provided between the high pressure chamber and the low pressure chamber, and further includes a check valve that suppresses oil from flowing from the high pressure chamber to the low pressure chamber, and the spring closes the check valve. Energize in the direction.

  According to the said structure, the force which a spring pushes up a non-return valve can be strong at the time of low rotation, and can be weakened at the time of high rotation. By increasing the force for pushing up the check valve, the check valve can be easily closed and the plunger can be pushed up easily. As a result, the pushing up of the plunger can be promoted at a low rotation and suppressed at a high rotation.

  According to the present invention, it is possible to obtain a hydraulic lash adjuster that operates stably both when the internal combustion engine is rotating at low speed and at high speed.

  Hereinafter, an embodiment of a hydraulic lash adjuster according to the present invention will be described. Note that the same or corresponding parts are denoted by the same reference numerals, and the description thereof may not be repeated.

  FIG. 1 is a front view showing a valve operating mechanism to which a hydraulic lash adjuster according to one embodiment of the present invention is applied. 2 is a perspective view partially showing a variable valve lift mechanism included in the valve operating mechanism shown in FIG. In FIG. 2, a part is broken and shown so that the internal structure can be clearly understood.

  Referring to FIGS. 1 and 2, the valve operating mechanism includes a variable valve lift mechanism 10. The variable valve lift mechanism 10 is a mechanism that varies the valve lift amount of a valve of the internal combustion engine (in the present embodiment, the intake valve 11). The internal combustion engine may be a gasoline engine or a diesel engine. The internal combustion engine is mounted on a vehicle.

  The variable valve lift mechanism 10 is provided in the cylinder head of the internal combustion engine. In the cylinder head, a cam shaft 12 on which a cam 13 is formed, a rocker arm 16 that is pivotally supported, and an intake valve 11 that is driven to open and close according to the rocking of the rocker arm 16 are disposed. The variable valve lift mechanism 10 includes a drive shaft 20 that extends in one direction, a support pipe 18 that covers the outer peripheral surface of the drive shaft 20, and an input that is arranged side by side in the axial direction of the drive shaft 20 on the outer peripheral surface of the support pipe 18. An arm 14 and a swing cam 15 are provided.

  In this internal combustion engine, each cylinder is provided with a pair of intake valves 11 and a rocker arm 16, and the pair of intake valves 11 are opened and closed by a single cam 13. The variable valve lift mechanism 10 is provided with one input arm 14 corresponding to one cam 13 provided in each cylinder. Two swing cams 15 are provided on both sides of the input arm 14 corresponding to each of the pair of intake valves 11 provided in each cylinder.

  The support pipe 18 is formed in a hollow cylindrical shape and is disposed in parallel to the camshaft 12. The support pipe 18 is fixed to the cylinder head so as not to move or rotate in the axial direction. A drive shaft 20 is inserted into the support pipe 18 so as to be slidable in the axial direction. An input arm 14 and two swing cams 15 are provided on the outer peripheral surface of the support pipe 18 so as to be swingable about the axis of the drive shaft 20 and not to move in the axial direction. Yes.

  The input arm 14 includes an arm portion 14A that protrudes in a direction away from the outer peripheral surface of the support pipe 18, and a roller portion 14B that is rotatably connected to the tip of the arm portion 14A. The input arm 14 is provided so that the roller portion 14 </ b> B can be disposed at a position where it can contact the cam 13.

  The swing cam 15 has a substantially triangular nose portion 15A that protrudes in a direction away from the outer peripheral surface of the support pipe 18. A cam surface 15B that is curved in a concave shape is formed on one side (the lower side in FIG. 1) of the nose portion 15A. The intake valve 11 is provided with a valve spring. By the urging force, the roller 16A rotatably attached to the rocker arm 16 is pressed against the cam surface 15B.

  The input arm 14 and the swing cam 15 integrally swing about the axis of the drive shaft 20. Therefore, when the camshaft 12 rotates, the input arm 14 in contact with the cam 13 swings, and the swing cam 15 swings in conjunction with the movement of the input arm 14. The movement of the swing cam 15 is transmitted to the intake valve 11 through the rocker arm 16, and the intake valve 11 is driven to open and close.

  The variable valve lift mechanism 10 further includes a mechanism for changing the relative phase difference between the input arm 14 and the swing cam 15 around the axis of the support pipe 18, and by this mechanism, the valve lift of the intake valve 11 is changed. Change the amount accordingly. That is, if the relative phase difference between the two is increased, the swing angle of the rocker arm 16 with respect to the swing angle of the input arm 14 and the swing cam 15 is increased, and the valve lift amount of the intake valve 11 is increased. If the relative phase difference between the two is reduced, the swing angle of the rocker arm 16 with respect to the swing angle of the input arm 14 and the swing cam 15 is reduced, and the valve lift amount of the intake valve 11 is reduced.

  Next, the mechanism for changing the relative phase difference will be described in more detail. As shown in FIG. 2, the space defined between the input arm 14 and the two swing cams 15 and the outer peripheral surface of the support pipe 18 is rotatable with respect to the support pipe 18 and has a shaft. A slider gear 17 supported so as to be slidable in the direction is accommodated.

  The slider gear 17 is provided with a helical gear 17 </ b> B in which a right-hand spiral helical spline is formed at the central portion in the axial direction. Further, the slider gear 17 is provided with helical gears 17C each having a left-hand spiral helical spline formed on the opposite sides of the helical gear 17B.

  On the other hand, helical splines corresponding to the helical gears 17B and 17C are formed on the surfaces of the input arm 14 and the two swing cams 15 that define a space for accommodating the slider gear 17, respectively. That is, the input arm 14 is formed with a right-hand spiral helical spline, and the helical spline meshes with the helical gear 17B. Further, the swing cam 15 is formed with a left-handed spiral helical spline, and the helical spline meshes with the helical gear 17C.

  The slider gear 17 is formed with a long hole 17A extending between the one helical gear 17C and the helical gear 17B and extending in the circumferential direction. In addition, a long hole 18A extending in the axial direction is formed in the support pipe 18 so as to overlap a part of the long hole 17A. The drive shaft 20 inserted into the support pipe 18 is integrally provided with a locking pin 20A that protrudes through the overlapping portion of the two long holes 17A and 18A.

  When the drive shaft 20 moves in the axial direction, the slider gear 17 is pushed by the locking pin 20A, so that the helical gears 17B and 17C move in the axial direction of the drive shaft 20 at the same time. In response to the movement of the helical gears 17B and 17C, the input arm 14 and the swing cam 15 that are spline-engaged with the helical gears 17B and 17C do not move in the axial direction. To turn. At this time, since the input arm 14 and the swing cam 15 have the opposite directions of the formed helical splines, the rotation directions are opposite to each other. As a result, the relative phase difference between the input arm 14 and the swing cam 15 changes, and the valve lift amount of the intake valve 11 is changed as already described.

  FIG. 3 is a side sectional view of the hydraulic lash adjuster 30. Referring to FIG. 3, the hydraulic lash adjuster 30 has a body 31. In the body 31, a plunger spring 32, a ball retainer 33, a check ball spring 34, a check ball 35, and a plunger 36 are disposed. A high pressure chamber 37 is formed between the bottom of the body 31 and the bottom of the plunger 36, and a low pressure chamber 38 is formed inside the plunger 36. The high pressure chamber 37 is filled with oil for lubricating the internal combustion engine. The high pressure chamber 37 and the low pressure chamber 38 communicate with each other via a communication passage 39 formed in a partition portion 39A located at the lower portion of the plunger 36, and the body 31 and the plunger 36 are formed in the low pressure chamber 38. Oil is supplied through the oil holes 31A and 36A. The oil supplied to the low pressure chamber 38 is discharged from an oil pump that is driven as the internal combustion engine is operated, and reaches the oil holes 31A and 36A through the oil passage.

  A plunger spring 32 and a ball retainer 33 are disposed in the high pressure chamber 37. Then, the urging force of the plunger spring 32 acts on the plunger 36 via the ball retainer 33, so that the plunger 36 is always urged in a direction protruding from the body 31. In the high pressure chamber 37, a check ball spring 34 and a check ball 35 are disposed between the ball retainer 33 and the bottom of the plunger 36. The urging force of the check ball spring 34 acts on the check ball 35 so that the check ball 35 is held at a position where the communication path 39 is blocked.

  Therefore, after the intake valve 11 starts to close during the operation of the internal combustion engine, when the cam 13 tries to move away from the swing cam 15, the plunger spring 32 extends and the plunger 36 advances from the body 31 (that is, the hydraulic lash adjuster). 30 stretches). The rocker arm 16 is pressed against the swing cam 15 by the plunger 36. Then, the swing cam 15 is pressed against the cam 13 side. As described above, the swing cam 15 is displaced following the cam 13, thereby suppressing a clearance between the cam 13 and the swing cam 15.

  When the hydraulic lash adjuster 30 is extended as described above, the pressure in the high pressure chamber 37 decreases as the volume of the high pressure chamber 37 increases, and the force based on the differential pressure between the high pressure chamber 37 and the low pressure chamber 38 is checked. It acts on the ball 35. Then, when the check ball 35 is displaced to a position where the blocking of the communication path 39 is released against the urging force of the check ball spring 34 by the force based on the differential pressure, oil flows from the low pressure chamber 38 to the high pressure chamber 37. Become. Thereafter, when the magnitude of the force based on the differential pressure becomes equal to or less than the biasing force of the check ball spring 34, the check ball 35 is returned to a position where the communication path 39 is blocked.

  On the other hand, when the swing cam 15 is pushed by the cam 13 when the intake valve 11 is opened, the force is transmitted to the plunger 36 via the rocker arm 16, and the plunger 36 tends to enter the body 31. At this time, since the communication passage 39 is blocked by the check ball 35, oil outflow from the high pressure chamber 37 to the low pressure chamber 38 is suppressed. The oil filled in the high pressure chamber 37 suppresses the movement of the plunger 36 in the direction of reducing the volume of the high pressure chamber 37, in other words, the plunger 36 entering the body 31.

  When the plunger 36 is going to enter the body 31 in this way, the oil in the high pressure chamber 37 slightly passes between the inner peripheral surface of the body 31 and the outer peripheral surface of the plunger 36, and the hydraulic lash adjuster 30. The plunger 36 slightly sinks into the body 31. However, the approach of the plunger 36 into the body 31 is recovered by the operation of the hydraulic lash adjuster 30 after the intake valve 11 starts to close.

  FIG. 4 is a diagram showing a configuration of an oil passage that supplies oil to the hydraulic lash adjuster 30. Referring to FIG. 4, the cylinder head is provided with a plurality of hydraulic lash adjusters 30, and these hydraulic lash adjusters 30 are connected to each other by a lash adjuster oil passage 50. The lash adjuster oil passage 50 is connected to the main oil passage 40. The main oil passage 40 connects an oil pan 41, an oil pump 42, an oil filter 43, and a block 44, and becomes a main passage for engine oil. Oil in the main oil passage 40 is circulated by an oil pump 42. A valve 49 is provided at the boundary between the main oil passage 40 and the lash adjuster oil passage 50, and the oil flow can be cut, connected, and switched. A hydraulic pressure sensor 60 is provided at the end of the lash adjuster oil passage 50. The main oil passage 40 also lubricates the variable valve timing mechanism inlet 45, the chain 46 and the variable valve timing mechanism outlet 47. The main oil passage 40 is also led to a shower pipe 48 provided above the valve operating system parts. Further, the cam bearing 12 </ b> A is also lubricated by the main oil passage 40.

  When the hydraulic lash adjuster 30 described above is actually operated, the temperature of the oil is low when the internal combustion engine is running at a low speed, and thus the viscosity of the oil is high. For this reason, the valve closing of the check ball 35 tends to be delayed, and a stronger force is required to push up the plunger 36.

  On the other hand, when the intake valve 11 is temporarily separated from the rocker arm 16 due to valve surging or the like during high rotation of the internal combustion engine, the plunger 36 of the hydraulic lash adjuster 30 advances and fills in the body 31 so as to fill the gap. Oil flows in. This may cause a phenomenon (pump up) in which the hydraulic lash adjuster 30 extends excessively. When pump-up occurs, the oil that has flowed into the body 31 prevents the plunger 36 from entering the body 31, resulting in a state where the intake valve 11 cannot be completely closed (incomplete valve closing state). There is a case. When an incomplete valve closing state occurs, combustion gas leaks from the combustion chamber to the intake path and the exhaust path, and there is a concern that the reliability of the intake system parts and the exhaust system parts may decrease and the output torque of the engine may decrease. Therefore, when the internal combustion engine rotates at a high speed, it is required to push up the plunger 36 with a relatively weak force.

  On the other hand, in the hydraulic lash adjuster 30 according to the present embodiment, a plunger spring 32 is used in which the urging force becomes strong at low temperatures and the urging force becomes weak at high temperatures. More specifically, the plunger spring 32 is made of a shape memory alloy so that the spring is long at low temperatures and short at high temperatures. By doing in this way, the force which pushes up the plunger 36 at high temperature can be strengthened, while the force which pushes up the plunger 36 at high temperature can be weakened. As a result, it is possible to suppress both the stretch of the hydraulic lash adjuster 30 during low rotation and the pump-up during high rotation.

  In the hydraulic lash adjuster 30, a check ball spring 34 may be used in which the urging force is increased at low temperatures and the urging force is decreased at high temperatures. More specifically, the check ball spring 34 is formed of a shape memory alloy so that the spring is long at low temperatures and short at high temperatures. By doing so, the force that pushes up the check ball 35 is strengthened at low temperatures to eliminate the delay in closing the valve, while the force that pushes up the check ball 35 is weakened at high temperatures to delay the valve closing and hydraulic lash Excessive extension of the adjuster 30 can be suppressed. As a result, it is possible to suppress both the stretch of the hydraulic lash adjuster 30 during low rotation and the pump-up during high rotation.

  In other words, the contents described above are as follows. In other words, the hydraulic lash adjuster 30 according to the present embodiment defines the high pressure chamber 37 and the low pressure chamber 38 and is fitted to the body 31 as a “housing” having an opening continuous with the low pressure chamber 37 and the opening of the body 31. Plunger 36 that comes into contact with the rocker arm 16 as a “separate member” and a plunger spring 32 and check as a “stretch member” that generates a force that promotes the pushing of the plunger 36 toward the rocker arm 16 by expanding and contracting. And a ball spring 34. The plunger spring 32 and the check ball spring 34 include a shape memory alloy, and are formed to be relatively long at a low temperature and relatively short at a high temperature. Only one of the plunger spring 32 and the check ball spring 34 may be configured to include a shape memory alloy.

  The hydraulic lash adjuster 30 includes a partition portion 39 </ b> A that partitions the high pressure chamber 37 and the low pressure chamber 38. The plunger spring 32 urges the partition portion 39 </ b> A toward the rocker arm 16.

  Further, the hydraulic lash adjuster 30 is provided between the high pressure chamber 37 and the low pressure chamber 38, and includes a check ball 35 as a “check valve” that suppresses the outflow of oil from the high pressure chamber 37 to the low pressure chamber 38. ing. The check ball spring 34 urges the check ball 35 toward the valve closing direction.

  In the present embodiment, the example of the valve operating mechanism including the variable valve lift mechanism has been described. However, the hydraulic lash adjuster 30 may be applied to a valve operating mechanism that does not include the variable valve lift mechanism. In this embodiment, an example of an intake system valve mechanism has been described. However, the hydraulic lash adjuster 30 may be applied to an exhaust system valve mechanism.

  According to the hydraulic lash adjuster 30 according to the present embodiment, the plunger push-up force can be increased during low rotation of the internal combustion engine, while the plunger push-up force can be reduced during high rotation of the internal combustion engine. As a result, a hydraulic lash adjuster that operates stably at both low and high speeds of the internal combustion engine can be obtained.

  Although the embodiments of the present invention have been described above, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a front view showing a valve operating mechanism to which a hydraulic lash adjuster according to one embodiment of the present invention is applied. It is a perspective view which shows partially the valve lift variable mechanism contained in the valve operating mechanism shown by FIG. It is side surface sectional drawing of the hydraulic lash adjuster shown by FIG. It is the figure which showed the structure of the oil path which supplies oil to the hydraulic lash adjuster shown by FIG.

Explanation of symbols

  10 Valve Lift Variable Mechanism, 11 Intake Valve, 12 Cam Shaft, 12A Cam Bearing, 13 Cam, 14 Input Arm, 14A Arm, 14B Roller, 15 Swing Cam, 15A Nose, 15B Cam Surface, 16 Rocker Arm, 16A Roller, 17 Slider gear, 17A long hole, 17B, 17C Helical gear, 18 Support pipe, 18A long hole, 20 Drive shaft, 30 Hydraulic lash adjuster, 31 Body, 31A Oil hole, 32 Plunger spring, 33 Ball retainer, 34 Check ball Spring, 35 Check ball, 36 Plunger, 36A Oil hole, 37 High pressure chamber, 38 Low pressure chamber, 39 Communication passage, 39A Partition, 40 Main oil passage, 41 Oil pan, 42 Oil pump, 43 Oil filter, 4 Block 45 the variable valve timing mechanism inlet, 46 a chain, 47 a variable valve timing mechanism outlet, 48 shower pipes, 49 valves, 50 lash adjuster oil passage 60 hydraulic pressure sensor.

Claims (4)

A housing that defines a high-pressure chamber and a low-pressure chamber, and has an opening continuous with the low-pressure chamber;
A plunger fitted into the opening and in contact with another member;
An expansion / contraction member that generates a force that promotes push-up of the plunger toward the other member by expanding and contracting;
The elastic lash adjuster is formed so that the elastic member is relatively long at a low temperature and relatively short at a high temperature.   The hydraulic lash adjuster according to claim 1, wherein the elastic member is a spring including a shape memory alloy. A partition that partitions the high pressure chamber and the low pressure chamber;
The hydraulic lash adjuster according to claim 2, wherein the spring biases the partition portion toward the separate member. A check valve provided between the high-pressure chamber and the low-pressure chamber, further comprising a check valve that suppresses the outflow of oil from the high-pressure chamber to the low-pressure chamber;
The hydraulic lash adjuster according to claim 2, wherein the spring biases the check valve in a valve closing direction.

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