Lash adjuster

Abstract

To provide a lash adjuster capable of suppressing occurrence of air entrainment.SOLUTION: A lash adjuster 10 includes: a cylindrical body; a plunger which has a bottom and a peripheral wall, which is slidably arranged in the body, which forms a high-pressure chamber between the body and it, which forms a low-pressure chamber in an inside thereof, and which forms a valve hole communicating the high-pressure chamber with the low-pressure chamber in the bottom; and a valve element 28 which is disposed in the high-pressure chamber and opens and closes the valve hole 26 by coming into contact with or being separated from a valve seat 26A on a lower surface of the bottom 18 of the plunger 12. In a cross sectional view of the bottom 18 cut along a vertical direction at a position passing through a center axis C2 of the valve hole 26, a valve seat 26AR of one of portions on both sides of the valve hole 26 on the bottom 18 is positioned on an upper side relative to a valve seat 26AL of the other portion.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a lash adjuster.

Background Art

[0002] As a hydraulic lash adjuster used in a valve operating device of an internal combustion engine, the one described in Patent Document 1 is known. This device includes a cylindrical body and a plunger slidably disposed within the body, and supports a rocker arm at the upper end of the plunger. The interior of the plunger is a low-pressure chamber, the lower part of the body is a high-pressure chamber partitioned by the bottom wall of the plunger, and a valve hole is opened in the bottom wall of the plunger. The hydraulic oil supplied from the oil supply passage of the cylinder head is stored in the low-pressure chamber through the communication hole in the peripheral wall of the body and the communication hole in the peripheral wall of the plunger, and the high-pressure chamber is also filled with hydraulic oil through the valve hole. Further, a spherical valve body capable of closing the valve hole is accommodated in the high-pressure chamber.

[0003] When the pressing force applied from the rocker arm side becomes weaker than the biasing force of the spring in the high-pressure chamber, the plunger is pushed up and extended by the action of the spring, and the valve clearance is adjusted. At this time, inside the lash adjuster, the hydraulic oil in the low-pressure chamber flows into the high-pressure chamber through the valve hole while pushing down the valve body in the high-pressure chamber. Thereby, the high-pressure chamber maintains a state of being filled with hydraulic oil inside. On the other hand, when the pressing force applied to the plunger becomes stronger, the valve body closes the valve hole, so that the high-pressure chamber becomes airtight and the descent of the plunger is restricted. Thus, by rigidifying the body and the plunger due to the pressure increase in the high-pressure chamber, the lash adjuster can stably support the rocker arm.

[0004] The hydraulic fluid supplied from the cylinder head's oil supply passage may contain air bubbles. These air bubbles can enter the high-pressure chamber along with the hydraulic fluid when the lash adjuster extends. If air lock occurs in the lash adjuster, causing it to accumulate in the high-pressure chamber, the lash adjuster will contract when subjected to pressure from the rocker arm. In this case, the lash adjuster cannot become sufficiently rigid, and its function of stably supporting the rocker arm is impaired. For this reason, Patent Document 1 describes a design in which a tapered surface that rises towards the valve hole is formed on the underside of the plunger's bottom to collect the air in the high-pressure chamber around the valve seat, making it easier for the accumulated air in the high-pressure chamber to escape. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-189926 [Overview of the project] [Problems that the invention aims to solve]

[0006] Thus, lash adjusters require technology that can effectively discharge air from the high-pressure chamber to suppress the occurrence of air lock-up.

[0007] This disclosure aims to provide a rush adjuster that can suppress the occurrence of air entrapment. [Means for solving the problem]

[0008] The lash adjuster according to this disclosure comprises a cylindrical body, a plunger having a bottom portion and a peripheral wall portion and slidably disposed within the body in the axial direction, forming a high-pressure chamber between itself and the body and a low-pressure chamber inside, and having a valve hole in the bottom portion that connects the high-pressure chamber and the low-pressure chamber, and a valve body disposed within the high-pressure chamber that opens and closes the valve hole by moving toward and away from a valve seat formed on the opening edge of the valve hole on the lower surface of the bottom portion, wherein in a cross-sectional view obtained by cutting the bottom portion vertically at a position passing through the central axis of the valve hole, the height of the valve seat in one portion of the portions located on both sides of the valve hole in the bottom portion is located above the height of the valve seat in the other portion. [Effects of the Invention]

[0009] The lash adjuster of this disclosure, by providing a height difference in the valve seat, can collect air that has gathered around the valve seat to a higher position, thereby promoting its discharge from the valve hole. For this reason, the lash adjuster of this disclosure can suppress the occurrence of air entrapment. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing the entire valve train, including the lash adjuster, according to Example 1. [Figure 2] This is a cross-sectional view of a lash adjuster according to Example 1, showing the valve in the closed state. [Figure 3] This is an enlarged cross-sectional view of the main part of the lash adjuster according to Example 1, showing the valve in the open state. [Figure 4] This is an enlarged cross-sectional view of the main part of the lash adjuster according to Example 1, showing a half-open valve state where the valve body is making contact with the valve seat on one side. [Modes for carrying out the invention]

[0011] [Description of Embodiments in this Disclosure] Preferred forms of this disclosure are shown below.

[0012] The opening edge of the valve hole has an inclined edge that slopes horizontally from one end of the valve seat in one portion to the other end of the valve seat in the other portion, and the valve hole penetrates at the bottom in a direction perpendicular to the inclined edge. In this case, a valve seat that can suitably contact a spherical valve body can be easily formed.

[0013] The lower surface of the bottom portion preferably has a tapered surface that slopes upward from the outer circumference toward the valve hole. In this case, the air on the lower surface of the bottom portion can be easily collected around the valve seat.

[0014] It is preferable to include a delay unit that generates a time lag between the state in which the valve body first contacts the valve seat and the state in which the valve is closed. In this case, the discharge of air can be further promoted during the time lag.

[0015] The delay portion is provided with a guide located in the high-pressure chamber that guides the movement of the valve body in conjunction with the opening and closing of the valve hole, and the delay portion is configured such that the center point of the valve body in the closed state is offset with respect to the central axis of the guide of the valve body by the guide until the valve body first contacts the valve seat. In this case, a configuration that can suitably generate a time lag as the delay portion can be easily realized.

[0016] Embodiments of this disclosure will be described below with reference to the drawings. For convenience, in the following description, the direction of extension and retraction of the lash adjuster will be defined as the vertical direction. That is, the vertical direction will be defined as upward and downward as shown in each figure. The lash adjuster according to this disclosure is basically intended to be installed with the extension and retraction direction being the vertical direction. However, the direction defined herein does not limit the installation direction of the lash adjuster according to this disclosure.

[0017] <Example 1> Embodiment 1 of this embodiment will be described with reference to Figures 1 to 4. The lash adjuster 10 of Embodiment 1 is provided in the valve train of an internal combustion engine of an automobile.

[0018] As shown in FIG. 1, the valve device includes a valve 80 that opens and closes the intake or exhaust port 91 of the cylinder head 90, a cam 71 provided on a camshaft 70 that rotates in synchronization with the engine and operates the valve 80, and a rocker arm 60 that transmits the movement of the cam 71 to the valve 80. The lash adjuster 10 is fitted into the mounting hole 93 of the cylinder head 90 and has a function of automatically adjusting the valve clearance (the clearance between the cam 71 and the rocker arm 60) hydraulically.

[0019] The valve 80 has a valve stem 81, and the valve stem 81 is slidably inserted into a valve guide 92 of the cylinder head 90. The lower end portion of the valve 80 is a disc-shaped valve body 82 facing the intake or exhaust port 91. A valve spring 85 is provided around the valve stem 81. The valve 80 is biased by the valve spring 85 in a direction in which the valve body 82 closes the intake or exhaust port 91.

[0020] One end of the rocker arm 60 is supported by a support portion 20 (to be described later) of the lash adjuster 10, the other end is disposed in contact with the upper end portion of the valve stem 81, and a roller 61 that contacts the cam 71 installed above is rotatably provided between the one end and the other end.

[0021] As shown in FIG. 1, the lash adjuster 10 is inserted into a mounting hole 93 formed in the upper surface of the cylinder head 90 with its axis oriented in the vertical direction. An oil supply passage 94 of the cylinder head 90, which is a flow path for the hydraulic oil supplied to the lash adjuster 10, communicates with the inner surface of the mounting hole 93.

[0022] As shown in Figure 2, the lash adjuster 10 has a cylindrical shape as a whole, extending along the central axis C. The lash adjuster 10 comprises a bottomed cylindrical body 11 and a bottomed cylindrical plunger 12 housed within the body 11 so as to be reciprocally movable (reciprocally sliding) in the direction of the central axis C of the lash adjuster 10. The lash adjuster 10 extends when the plunger 12 moves in a direction that protrudes from the body 11, and contracts when the plunger 12 moves in the opposite direction. The body 11 consists of a disc-shaped bottom wall 13 and a circumferential wall 14 that rises from the outer circumference of the bottom wall 13. An outer circumferential groove 15 is provided around the entire circumference of the outer circumferential surface of the circumferential wall 14 of the body 11. In addition, the circumferential wall 14 of the body 11 is provided with a body oil hole 16 that penetrates radially (in the wall thickness direction of the circumferential wall 14 of the body 11) from the groove back surface to the inner circumferential surface of the outer circumferential groove 15. An inner circumferential groove 17 is provided around the entire circumference of the inner circumferential surface of the peripheral wall 14 of the body 11, corresponding to the height position of the opening on the inner circumferential surface side of the body oil hole 16. A retainer 50 is attached to the upper end of the peripheral wall 14 to restrict the upward movement of the plunger 12.

[0023] The plunger 12 is housed in the body 11 with its upper end protruding from the upper end of the body 11. The plunger 12 consists of a disc-shaped bottom portion 18 that is slightly smaller than the bottom wall 13 of the body 11, and a peripheral wall portion 19 that rises from the outer circumference of the bottom portion 18 and tapers to a roughly hemispherical shape at the upper end. The radial center of the bottom portion 18 is located on the central axis C of the lash adjuster 10. The upper end of the peripheral wall portion 19 of the plunger 12 is a support portion 20, and one end of the rocker arm 60 is slidably supported on the hemispherical outer surface of the support portion 20 (see Figure 1). A top hole 21 is provided at the upper end of the support portion 20, penetrating vertically. The inside of the plunger 12 is configured as a low-pressure chamber 22 partitioned by the bottom portion 18 and the peripheral wall portion 19. A concave recess 18A is formed on the lower surface of the bottom portion 18. A retainer 29, which will be described later, is press-fitted into the recess 18A.

[0024] The upper end of the peripheral wall portion 19 of the plunger 12 is provided with an annular band portion 23 that protrudes outward in a thick manner along its entire circumference. The outer circumferential surface of the annular band portion 23 is capable of substantially liquid-tight contact (sliding contact) with the inner circumferential surface of the upper end of the peripheral wall 14 of the body 11 along its vertical direction. The outer circumferential surface of the peripheral wall portion 19 of the plunger 12 is provided with a plunger circumferential groove 24 that defines the lower end surface of the annular band portion 23 along its entire circumference.

[0025] Furthermore, the circumferential wall portion 19 of the plunger 12 is provided with a plunger oil hole 25 that penetrates radially (in the wall thickness direction of the circumferential wall portion 19 of the plunger 12) from the groove back surface to the inner circumferential surface of the plunger circumferential groove 24. The plunger oil hole 25 is positioned above the body oil hole 16. The diameter of the plunger oil hole 25 is larger than the diameter of the body oil hole 16.

[0026] The hydraulic fluid supplied from the oil supply passage 94 of the cylinder head 90 is stored in the low-pressure chamber 22 after passing through the outer circumferential groove 15, the body oil hole 16, the plunger circumferential groove 24, and the plunger oil hole 25. In this case, even if the body 11 rotates within the mounting hole 93 of the cylinder head 90, the hydraulic fluid flows to the body oil hole 16 via the outer circumferential groove 15, and even if the plunger 12 rotates within the body 11, the hydraulic fluid flows to the plunger oil hole 25 via the plunger oil hole 25.

[0027] A valve hole 26 is formed in the bottom 18 of the plunger 12. The valve hole 26 has a circular cross-section. The valve hole 26 penetrates the bottom 18 vertically and connects the upper low-pressure chamber 22 and the lower high-pressure chamber 27, which will be described later. As shown in Figure 2, in this embodiment, the central axis C1 of the valve hole 26 is inclined with respect to the central axis C of the lash adjuster 10. The inclination angle of the central axis C1 of the valve hole 26 is, for example, 8° with respect to the central axis C (vertical direction) of the lash adjuster 10.

[0028] A valve seat 26A is formed at the opening edge of the valve bore 26 on the high-pressure chamber 27 side. The valve seat 26A curves outwards in an arc shape in cross-section as it extends downwards. In this embodiment, there is a difference in height between the valve seats 26A. Specifically, as shown in Figure 3, in a cross-sectional view obtained by cutting the bottom portion 18 of the valve seat 26A along the vertical direction at a point passing through the central axis C1 of the valve bore 26, the height of the right valve seat 26AR, which is one portion of the bottom portion 18 located on both sides of the valve bore 26, is higher than the height of the left valve seat 26AL, which is the other portion.

[0029] As shown in Figure 3, the lower edge 26B of the valve seat 26A, which is the opening edge of the valve hole 26, is formed at an angle with respect to the horizontal. As a result, the lash adjuster 10 of this embodiment has a configuration that provides a height difference in the valve seat 26A. As shown in the cross-sectional view in Figure 3, the lower edge 26B of the valve seat 26A is a straight line that slopes with respect to the horizontal from the right end of the right valve seat 26AR to the left end of the left valve seat 26AL. The lower edge 26B of the valve seat 26A is an example of an inclined edge according to this disclosure. The valve hole 26 penetrates the bottom 18 in a direction perpendicular to this lower edge 26B. In this embodiment, the angle of inclination of the lower edge 26B of the valve seat 26A with respect to the horizontal is, for example, 8°.

[0030] A tapered surface T is formed on the lower surface of the bottom portion 18. The tapered surface T is concave in a mortar shape around the valve seat 26A. The tapered surface T slopes upward from the outer peripheral edge of the bottom portion 18 toward the valve seat 26A. The tapered surface T maintains a uniform angle of, for example, 60° around the entire circumference with respect to the central axis C1 of the valve hole 26. Due to the inclined formation of the valve hole 26, there is a difference in height in the circumferential direction of the tapered surface T. In the case of Figure 3, the uppermost part of the tapered surface T is the connection part H with the lower end edge 26B of the valve seat 26AR. The lash adjuster 10 is configured such that air tends to accumulate in the high-pressure chamber 27 at this uppermost connection part H of the tapered surface T.

[0031] A high-pressure chamber 27 is formed in the lower part of the body 11 between it and the bottom 18 of the plunger 12. The high-pressure chamber 27 is provided with a valve body 28 that can close the valve hole 26 from the high-pressure chamber 27 side, a retainer 29 that holds the valve body 28, a first spring 31 consisting of a compression coil spring housed in the retainer 29 and biasing the valve body 28 toward the valve hole 26, and a second spring 32 consisting of a compression coil spring interposed between the outer peripheral edge of the retainer 29 and the bottom wall 13 of the body 11 and biasing the plunger 12 upward. The valve body 28 is constantly biased upward by the first spring 31. The valve body 28 moves up and down in accordance with the balance between the hydraulic pressure fluctuations in the high-pressure chamber 27 and the biasing force of the first spring 31, opening and closing the valve hole 26. When the valve hole 26 is open, the lash adjuster 10 allows the hydraulic fluid from the low-pressure chamber 22 to flow through the valve hole 26 into the high-pressure chamber 27.

[0032] The retainer 29 has a so-called hat-shaped (brimmed cap-shaped) external form that opens upward. The retainer 29 houses the valve body 28 in its internal space. The retainer 29 houses the valve body 28 while allowing the valve body 28 to move as the valve hole 26 opens and closes. The retainer 29 has multiple notches formed circumferentially and evenly spaced to connect the internal and external spaces and allow the inflow and outflow of hydraulic fluid. The retainer 29 has a cylindrical portion 29A that is bottomed and houses the valve body 28, and a flange-shaped portion 29B that extends outward from the upper end of the cylindrical portion 29A. The cylindrical portion 29A and the flange-shaped portion 29B are arranged coaxially on the central axis C2 of the retainer 29. The retainer 29 is press-fitted into the recess 18A at the outer peripheral edge of the flange-shaped portion 29B. The central axis C2 of the retainer 29 is located coaxially with the central axis C of the lash adjuster 10.

[0033] A spring seat 29C is formed at the lower end of the retainer 29. The lower end of the first spring 31 contacts the spring seat 29C. The retainer 29 and the first spring 31 are examples of guides according to this disclosure. The central axis C2 of the retainer 29 corresponds to the guide central axis according to this disclosure. The guide central axis is the central axis when the valve body 28 moves. The valve body 28 moves linearly along the central axis C2 of the retainer 29, which is the guide central axis, while being biased by the first spring 31, from the open state to the state in which it first contacts the valve seat 26A.

[0034] The first spring 31 is in contact with the spring seat 29C of the retainer 29 at its lower end. The lower end of the first spring 31 is positioned concentrically with the central axis C2 of the retainer 29. The first spring 31 is in contact with the valve body 28 at its upper end. The first spring 31 imparts a biasing force to the valve body 28 that biases it upward. The second spring 32 is interposed between the flange-like portion 29B of the retainer 29 and the bottom wall 13 of the body 11. The second spring 32 imparts a biasing force to the plunger 12 that biases it upward.

[0035] The lash adjuster 10 of this embodiment includes a delay section. The delay section generates a time lag from the state in which the valve body 28 first contacts the valve seat 26A until the valve is closed. As shown in Figure 4, in the lash adjuster 10, the delay section is configured to shift the position of the center point C3 of the valve body 28 in the closed state relative to the central axis C2 of the retainer 29, which serves as the guide central axis. As described above, the valve bore 26 is formed with its central axis C1 inclined with respect to the central axis C of the lash adjuster 10. In the lash adjuster 10, the inclination of the central axis C1 of the valve bore 26 is set such that the center point C3 of the valve body 28 in the closed state (indicated by the dashed line in Figure 4) is shifted relative to the central axis C2 of the retainer 29. As a result, when the valve body 28 first contacts the valve seat 26A, it can only partially contact the valve seat 26A and not completely close the valve bore 26, i.e., it can be in a state of partial contact. In the lash adjuster 10, the delay section is configured to create a time lag before reaching the closed valve state by causing the valve body 28 to make partial contact with the valve seat 26A.

[0036] Next, we will explain the basic operation of the Lash Adjuster 10. During normal operation of the internal combustion engine, the camshaft 70 and cam 71 rotate, and when the rocker arm 60 is pressed downward by the cam 71, the valve 80 is pushed down and opens. At this time, the support portion 20 is pressed against one end of the rocker arm 60. As a result, a force acts on the plunger 12 in the direction of sinking into the body 11. At this time, although the sinking of the plunger 12 is restricted because the valve hole 26 is closed by the valve body 28, the high-pressure chamber 27 receives a compressive force and the pressure rises. Then, the hydraulic fluid in the high-pressure chamber 27 flows between the peripheral wall portion 19 of the plunger 12 and the peripheral wall 14 of the body 11 and gradually flows out towards the plunger circumferential groove 24. As a result, the volume of the high-pressure chamber 27 gradually decreases, the plunger 12 sinks down relative to the body 11 (leak-down), and the overall length of the lash adjuster 10 is shortened. Furthermore, the increase in pressure in the high-pressure chamber 27 causes the body 11 and plunger 12 to become rigid, and the rocker arm 60 is stably supported by the lash adjuster 10.

[0037] As the camshaft 70 and cam 71 rotate further, the amount of lift by the cam 71 decreases from the state in which the cam 71 is pressing the rocker arm 60 downward, and the downward pressing force on the rocker arm 60 is relieved. As a result, the valve 80 closes due to the repulsive force of the valve spring 85. At this time, an upward force acts on the rocker arm 60 due to the valve spring 85. Therefore, the downward force acting on the support portion 20 is relieved. As a result, a force acts on the plunger 12 from the second spring 32 in the direction of advancing toward the rocker arm 60, so the plunger 12 is pushed up and maintains a state in which the support portion 20 is in contact with one end of the rocker arm 60. As a result, the rocker arm 60 is pressed against the cam 71. Also, as the plunger 12 advances toward the rocker arm 60, the volume of the high-pressure chamber 27 expands and the pressure in the high-pressure chamber 27 decreases. This creates a pressure difference between the high-pressure chamber 27 and the low-pressure chamber 22, causing the valve body 28 to separate from the valve seat 26A and open the valve hole 26, allowing hydraulic fluid to flow from the low-pressure chamber 22 to the high-pressure chamber 27. As a result, the overall length of the lash adjuster 10 is extended. In this way, the lash adjuster 10 supports the rocker arm 60 in the correct position in accordance with the rotation of the cam 71, thereby adjusting the clearance between the cam 71 and the rocker arm 60 to be virtually zero.

[0038] Next, we will explain the function and effects of the Lash Adjuster 10. If air bubbles enter the high-pressure chamber 27 along with the hydraulic fluid, there is a risk of so-called air entrapment occurring, where air pockets form within the high-pressure chamber 27. The lash adjuster 10 has a configuration in which there is a height difference in the valve seat 26A. Specifically, in a cross-sectional view obtained by cutting the bottom 18 of the plunger 12 along the vertical direction at a point passing through the central axis C1 of the valve hole 26, the height of the valve seat 26AR located on one side of the bottom 18, which is on either side of the valve hole 26, is higher than the height of the valve seat 26AL located on the other side. By providing a height difference in the valve seat 26A in this way, the lash adjuster 10 can collect the air that gathers around the valve seat 26A in the high-pressure chamber 27 near the higher valve seat 26AR. The air collected around the valve seat 26AR is suitably discharged to the low-pressure chamber 22 side through the valve hole 26 when the valve is open. Therefore, the lash adjuster 10 can effectively suppress the occurrence of air lock.

[0039] Furthermore, the valve seat 26A has a lower edge 26B, which is the opening edge of the valve hole 26, that is inclined with respect to the horizontal direction. The valve hole 26 penetrates the bottom 18 in a direction perpendicular to this lower edge 26B. As a result, even with a valve seat 26A that has a height difference, it is possible to easily form a circular contact surface similar to that of a conventional valve seat without a height difference. For example, in a valve hole that penetrates along the vertical direction, if the valve seat is formed inclined with respect to the horizontal direction, the shape of the opening edge of the valve hole where the valve seat is formed becomes elliptical. In this case, it is difficult to form a valve seat that can make contact with a spherical valve body without gaps. In contrast, if the valve hole 26 penetrates in a direction perpendicular to the lower edge 26B of the inclined valve seat 26A, the shape of the opening edge can be formed in a circular shape as in the conventional case, so that the spherical valve body 28 can be suitably brought into contact with the entire surface of the valve seat 26A.

[0040] Furthermore, the lash adjuster 10 has a tapered surface T formed on the lower surface of the bottom portion 18. The tapered surface T is formed with an upward slope from the outer peripheral edge of the bottom portion 18 toward the valve seat 26A. As a result, the lash adjuster 10 can collect the air on the lower surface of the bottom portion 18 in the high-pressure chamber 27 toward the valve hole 26. In addition, the valve hole 26 in the lash adjuster 10 is formed with an inclination of the central axis C1, and the tapered surface T is formed at a uniform angle over the entire circumference with respect to this central axis C1. As a result, the connection portion H with the lower end edge 26B of the valve seat 26A is formed as the uppermost part of the tapered surface T in the lash adjuster 10. With this configuration, the lash adjuster 10 makes it easier for air that has entered the high-pressure chamber 27 to collect at the connection portion H, which is the uppermost part. As a result, the discharge of air toward the low-pressure chamber 22 through the valve hole 26 is promoted.

[0041] Furthermore, the lash adjuster 10 of this embodiment is equipped with a delay section. The delay section generates a time lag from the state in which the valve body 28 first contacts the valve seat 26A until the valve is closed. The delay section of the lash adjuster 10 is configured such that the central axis C1 of the valve hole 26 is inclined with respect to the central axis C2 of the retainer 29, which acts as the guide central axis, so that the center point C3 of the valve body 28 in the closed state is misaligned with respect to the central axis C2 of the retainer 29. As a result, the lash adjuster 10 causes the valve body 28 to make uneven contact with the valve seat 26A, and can generate a suitable time lag between the open state and the closed state compared to conventional designs.

[0042] When the lash adjuster 10, which is in an extended state, retracts again, the volume of the high-pressure chamber 27 decreases, and the hydraulic fluid in the high-pressure chamber 27 flows out into the low-pressure chamber 22 through the open valve hole 26. While the valve hole 26 is open, the lash adjuster 10 can release the air accumulated in the high-pressure chamber 27 into the low-pressure chamber 22 along with the hydraulic fluid. The outflow of hydraulic fluid from the valve hole 26 continues until the valve hole 26 is closed by the valve body 28. Therefore, from the viewpoint of discharging air from the high-pressure chamber 27, it is preferable that the valve hole 26 remains open for a long time.

[0043] In this embodiment, the center point C3 of the valve body 28 in the closed state is positioned offset from the central axis C2 of the retainer 29, which is the guide central axis of the valve body 28 when it is away from the valve seat 26A. Therefore, as shown in Figures 3 and 4, the valve body 28 when it is away from the valve seat 26A has its center point C3 located on the central axis C2 of the retainer 29, which is the guide central axis, and moves linearly along this central axis C2 of the retainer 29. Subsequently, as shown in Figure 4, the valve body 28 partially contacts only the valve seat 26AL, which is in a relatively lower position on the valve seat 26A, and does not contact the valve seat 26AR, which is in a relatively higher position, i.e., it is in a state of one-sided contact. In this way, until it reaches the state of one-sided contact, the center point C3 of the valve body 28 moves upward along the central axis C2 of the retainer 29, which is the guide central axis.

[0044] On the other hand, while the valve body 28 is moving from a partially contacted state to a closed state, the center point C3 of the valve body 28 moves in a direction different from the direction of movement along the central axis C2 of the retainer 29. Specifically, the center point C3 of the valve body 28 moves away from the central axis C2 of the retainer 29 and reaches the central axis C1 of the valve hole 26 (see the center point C3 of the valve body 28 shown by the dashed line in Figure 4). In this way, the lash adjuster 10 changes the direction of movement of the valve body 28 before and after it enters a partially contacted state. As a result, the lash adjuster 10 can create a suitable time lag from the partially contacted state to the closed state.

[0045] For example, in a conventional lash adjuster, the central axes of the valve bore and the retainer are usually both located on the central axis of the lash adjuster. That is, in a conventional lash adjuster, the central axes of the valve bore and the retainer are located coaxially. Therefore, in a conventional lash adjuster, the center point of the valve body is located on the central axis of the valve bore, even when it is separated from the valve seat. Consequently, in a conventional lash adjuster where the central axes of the valve bore and the retainer are located coaxially, the valve body moves linearly along the central axis of the valve bore from the open state to the closed state.

[0046] In contrast, the lash adjuster 10 of this embodiment has a configuration in which the central axis C1 of the valve bore 26 is inclined with respect to the central axis C2 of the retainer 29, such that the central point C3 of the valve body 28 in the closed state is misaligned with respect to the central axis C2 of the retainer 29, which serves as the guide central axis. As a result, the valve body 28 moves along the central axis C2 of the retainer 29, as in the conventional case, while being biased by the first spring 31, from the open state to the one-sided contact state where it first contacts the valve seat 26A. In the one-sided contact state with respect to the valve seat 26A, the valve body 28 is in contact with the valve seat 26AL, which is in a relatively lower position, and away from the valve seat 26AR, which is in a relatively higher position. Subsequently, further biased by the biasing force of the first spring 31, the valve body 28 makes overall contact with the valve seat 26A and reaches the closed state.

[0047] Thus, the valve body 28 moves linearly along the central axis C2 of the retainer 29, which serves as the guide axis, from the open state to the closed state, as in the conventional design. Subsequently, the valve body 28 changes its direction of movement by making contact with the valve seat 26A on one side. As a result, the lash adjuster 10 can relatively increase the time it takes to go from the open state to the closed state compared to the conventional design where the valve body moves linearly only, allowing more air to be discharged from the high-pressure chamber 27.

[0048] Furthermore, in the lash adjuster 10 of this embodiment, the connection portion H is the portion of the valve seat 26A that is connected to the part that closes the slowest between the partially contacted state and the closed state. Therefore, the lash adjuster 10 can effectively discharge the air accumulated around the connection portion H.

[0049] <Other examples> Other embodiments are briefly described below. (1) In the above embodiment 1, a configuration in which the opening edge of the valve hole has an inclined edge was illustrated as a way to provide a height difference in the valve seat, but this is not essential. In the above embodiment, a configuration in which the valve hole is perpendicular to the inclined edge was illustrated, but the valve hole may be inclined with respect to the inclined edge. The inclination angle of the inclined edge can be, for example, in the range of 5° to 10° with respect to the horizontal direction. Within this range, it is possible to achieve both ease of collecting air around the valve seat and ease of manufacturing. (2) In the above embodiment 1, a configuration in which the valve hole is inclined with respect to the central axis of the retainer was illustrated, but this is not essential. In the lash adjuster according to the present disclosure, the central axis of the valve hole may extend vertically along the central axis of the lash adjuster. When the valve hole is inclined, the inclination angle is not limited to the above embodiment 1. The inclination angle of the valve hole can be, for example, in the range of 5° to 10° with respect to the central axis of the lash adjuster. Within this range, it can be easily manufactured. (3) In the above embodiment 1, a tapered surface is shown on the lower surface of the bottom of the plunger, but this is not essential. When a tapered surface is formed on the lower surface of the bottom, the shape of the tapered surface is not limited to the above embodiment. The tapered surface may, for example, have an uneven angle in the circumferential direction with respect to the central axis of the valve hole. The tapered surface may, for example, have a uniform angle over the entire circumference in the circumferential direction with respect to an axis other than the central axis of the valve hole, such as the central axis of the lash adjuster. (4) In the above embodiment 1, a configuration in which the lash adjuster includes a delay section was illustrated, but this is not essential. If a delay section is included, its configuration only needs to be able to generate a time lag from the state in which the valve body first contacts the valve seat to the closed state, and is not limited to the configuration of the above embodiment. The delay section may be configured, for example, by offsetting one of the central axes of the retainer and the central axis of the valve hole, which are arranged coaxially with the central axis of the lash adjuster, relative to the other. [Explanation of Symbols]

[0050] 10...Lash adjuster 11…Body 12…Plunger 14...Peripheral wall 18...bottom 19...Peripheral wall part 22... Low-pressure room 26… Valve opening 26A…Valve seat 26AL... Valve seat (the valve seat of the other part) 26AR... Valve seat (one part of the valve seat) 26B...Lower edge (sloping edge) 27…High-pressure room 28… Valve body 29…Retainer (guide) 31…First spring (guide) C1...Central axis (central axis of the valve opening) C2... The central axis of the retainer (the central axis of the guide). C3…center point T...Tapered surface

Claims

1. A cylindrical body, A plunger having a bottom portion and a peripheral wall portion, slidably positioned within the body in the axial direction, forming a high-pressure chamber between itself and the body, and having a low-pressure chamber inside, with a valve hole in the bottom portion connecting the high-pressure chamber and the low-pressure chamber, A valve body is disposed within the high-pressure chamber and opens and closes the valve hole by moving toward and away from a valve seat formed on the opening edge of the valve hole on the lower surface of the bottom, A lash adjuster equipped with, In a cross-sectional view obtained by cutting the bottom portion vertically along a position passing through the central axis of the valve hole, the height of the valve seat in one portion of the bottom portion located on both sides of the valve hole is higher than the height of the valve seat in the other portion. A lash adjuster comprising a delay unit that generates a time lag from the state in which the valve body first contacts the valve seat to the closed state.

2. The opening edge of the valve hole has an inclined edge that slopes horizontally from one end of the valve seat of one portion to the other end of the valve seat of the other portion. The lash adjuster according to claim 1, wherein the valve hole penetrates the bottom portion in a direction perpendicular to the inclined edge.

3. The lash adjuster according to claim 1, wherein the lower surface of the bottom portion has a tapered surface that slopes upward from the outer circumference toward the valve hole.

4. The high-pressure chamber is provided with a guide that guides the movement of the valve body in conjunction with the opening and closing of the valve hole, The lash adjuster according to any one of claims 1 to 3, wherein the delay portion is configured to shift the center point of the valve body in the closed state relative to the guide central axis of the valve body by the guide until the valve body first contacts the valve seat.

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