Lash adjuster

Abstract

To provide a lash adjuster capable of suppressing occurrence of air entrainment.SOLUTION: A lash adjuster 10 opens and closes a valve hole 26 when a valve element 28 comes into contact with or is separated from a valve seat 26A on a lower surface of a bottom 18 of a plunger 12. A retainer 29 is fixed to the bottom 18 on a high-pressure chamber 27 side. The retainer 29 holds the valve element 28 while allowing movement of the valve element 28 accompanying the opening and closing of the valve hole 26. The lash adjuster 10 has a configuration in which a center axis C1 of the valve hole 26 and a center axis C2 of the retainer 29 are offset from each other as a delay unit for generating a time lag from a state in which the valve element 28 first contacts the valve seat 26 to a valve close state.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As a hydraulic lash adjuster used in a valve gear of an internal combustion engine, the one described in Patent Document 1 is known. This one includes a cylindrical body and a plunger disposed slidably in the axial direction within the body, and supports a rocker arm at the upper end portion of the plunger. The inside of the plunger is a low-pressure chamber, and the lower part of the body is a high-pressure chamber partitioned by the bottom wall of the plunger. A valve hole is opened in the bottom wall of the plunger. In the low-pressure chamber, hydraulic oil supplied from an oil supply passage of a cylinder head is stored through a communication hole in the peripheral wall of the body and a 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. As a result, 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, when the body and the plunger are rigidified 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, 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, and a guide disposed within the high-pressure chamber that guides the movement of the valve body accompanying the opening and closing of the valve hole, and is characterized in that it comprises a delay portion that generates a time lag from the state in which the valve body first contacts the valve seat to the closed valve state. [Effects of the Invention]

[0009] The lash adjuster of this disclosure, by having a delay section, can extend the time the valve hole is open compared to conventional models, thereby promoting the discharge of air from the high-pressure chamber. As a result, 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. [Figure 5] This is an enlarged cross-sectional view of the main part of the lash adjuster according to Example 2, showing a half-open valve state where the valve body is making contact with the valve seat on one side. [Figure 6] This is an enlarged cross-sectional view of the main part of a lash adjuster according to another embodiment, 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 delay portion may be configured by offsetting the central axis of the valve hole and the central axis of the guide for the valve body 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.

[0013] The delay portion may be configured by offsetting the central axis of the valve hole from the radial center of the bottom. In this case, only the position of the valve hole differs from the configuration of a conventional lash adjuster, and the delay portion can be realized with an even simpler configuration.

[0014] In a cross-sectional view obtained by cutting the bottom portion vertically along a point passing through the central axis of the valve hole, it is preferable that the height of the valve seat in one portion of the bottom portion located on either side of the valve hole is higher than the height of the valve seat in the other portion. In this case, the difference in height of the valve seats makes it easy to create a time lag from the state in which the valve body first contacts the valve seat to the closed state. Furthermore, by providing a difference in height of the valve seats, the air in the high-pressure chamber can be collected around the valve seat located on the upper side. As a result, by configuring the valve body to first contact the valve seat located on the lower side and then contact the valve seat located on the upper side to reach the closed state, the discharge of the air collected around the valve seat located on the upper side during the time lag can be promoted.

[0015] 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, 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 in a configuration in which there is a height difference in the valve seat.

[0016] The lower surface of the one part may be inclined upward from the outer peripheral edge of the bottom portion toward the valve seat. In this case, the air on the lower surface of the bottom portion can be raised along the inclination and collected near the valve seat. As a result, the discharge of air from the valve hole can be further promoted.

[0017] Embodiments of the present disclosure will be described below with reference to the drawings. In the following description, for convenience, the direction in which the lash adjuster expands and contracts is defined as the vertical direction. That is, for the vertical direction, the directions shown in the respective drawings are directly defined as upward and downward. The lash adjuster according to the present disclosure is basically assumed to be installed with the expansion and contraction direction as the vertical direction. However, the direction defined here does not limit the installation direction of the lash adjuster according to the present disclosure.

[0018] <Example 1> Example 1 according to the present embodiment will be described based on FIGS. 1 to 4. The lash adjuster 10 of Example 1 is provided in the valve operating device of an internal combustion engine (engine) of an automobile.

[0019] As shown in FIG. 1, the valve operating device includes a valve 80 that opens and closes an intake or exhaust port 91 of a cylinder head 90, a cam 71 provided on a camshaft 70 that rotates in synchronization with the engine, and that 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.

[0020] 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 disk-shaped valve body 82 that faces the intake or exhaust port 91. A valve spring 85 is provided around the valve stem 81. The valve 80 is urged by the valve spring 85 in a direction in which the valve body 82 closes the intake or exhaust port 91.

[0021] The rocker arm 60 has one end supported by a support portion 20 (described later) of the lash adjuster 10, and the other end is arranged to abut on the upper end portion of the valve stem 81. A roller 61 that contacts a cam 71 installed above is rotatably provided between the one end and the other end.

[0022] As shown in FIG. 1, the lash adjuster 10 is inserted with its axis oriented in the vertical direction into a mounting hole 93 formed in the upper surface of the cylinder head 90. An oil supply passage 94 of the cylinder head 90, which is an oil passage for supplying hydraulic oil to the lash adjuster 10, communicates with the inner surface of the mounting hole 93.

[0023] As shown in FIG. 2, the lash adjuster 10 as a whole has a cylindrical shape extending along a central axis C. The lash adjuster 10 includes a bottomed cylindrical body 11 and a bottomed cylindrical plunger 12 that is reciprocally movable (reciprocally slidable) in the body 11 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 protruding from the body 11, and contracts when the plunger 12 moves in the opposite direction. The body 11 includes a disk-shaped bottom wall 13 and a peripheral wall 14 rising from the outer periphery of the bottom wall 13. An outer circumferential groove 15 is provided over the entire circumference on the outer peripheral surface of the peripheral wall 14 of the body 11. Further, a body oil hole 16 penetrating in the radial direction (the wall thickness direction of the peripheral wall 14 of the body 11) from the groove bottom surface of the outer circumferential groove 15 to the inner peripheral surface is provided in the peripheral wall 14 of the body 11. An inner circumferential groove 17 is provided over the entire circumference on the inner peripheral surface of the peripheral wall 14 of the body 11 corresponding to the height position of the opening on the inner peripheral surface side of the body oil hole 16. A retainer 50 for restricting the upward escape of the plunger 12 is attached to the upper end of the peripheral wall 14.

[0024] 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 serves as 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 is provided extending vertically through the bottom 18 along the central axis C of the lash adjuster 10. A valve seat 26A is formed at the opening edge of the valve hole 26 on the side of the high-pressure chamber 27, which will be described later. The valve seat 26A curves outwards in an arc shape in cross-section as it extends downwards. A recessed area 18A is formed on the lower surface of the bottom 18. A retainer 29, which will be described later, is press-fitted into the recess 18A. In this embodiment, the central axis C1 of the valve hole 26 is offset from the radial center of the bottom 18, i.e., from the central axis C of the lash adjuster 10.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] As described above, in this embodiment, the central axis C1 of the valve bore 26 is offset from the central axis C of the lash adjuster 10. Therefore, as shown in Figure 2, the center point C3 of the valve body 28 in the closed state is misaligned with respect to the central axis C of the lash adjuster 10. Consequently, the center point C3 of the valve body 28 in the closed state is also misaligned with respect to the central axis C2 of the retainer 29, which is the guide central axis. Thus, the configuration in which 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, which is the guide central axis, is an example of a delay section according to this disclosure.

[0034] 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.

[0035] 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.

[0036] 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. In the lash adjuster 10 of this embodiment, as a delay part according to this disclosure, a configuration is adopted in which the center point C3 of the valve body 28 in the closed state is offset from the center axis C2 of the retainer 29, which serves as the guide center axis. More specifically, a configuration is adopted in which the center axis C1 of the valve hole 26 and the center axis C2 of the retainer 29 are offset from each other. More specifically, the lash adjuster 10 offsets the center axis C1 of the valve hole 26 from the center axis C2 of the retainer 29, which is arranged concentrically with the center axis C of the lash adjuster 10. As a result, the lash adjuster 10 generates a time lag from the state in which the valve body 28 first contacts the valve seat 26A until the valve is closed, thereby promoting the discharge of air from the high-pressure chamber 27.

[0037] Figure 3 shows the state in the lash adjuster 10 of this embodiment where the valve body 28 is separated from the valve seat 26A. As shown in Figure 3, the center point C3 of the valve body 28, when separated from the valve seat 26A, is misaligned with respect to the central axis C1 of the valve hole 26. As described above, when the lash adjuster 10 is extended, a pressure difference is created between the high-pressure chamber 27 and the low-pressure chamber 22, causing a flow of hydraulic fluid to enter the high-pressure chamber 27 from the low-pressure chamber 22 through the valve hole 26. As a result, the valve body 28 separates from the valve seat 26A against the biasing force of the first spring 31 and is released from the influence of the position of the valve seat 26A.

[0038] When the valve body 28 is separated from the valve seat 26A, it is in contact only with the upper end of the first spring 31. When the valve body 28 is in contact only with the first spring 31, it is no longer under the influence of the position of the valve seat 26A and is in a position influenced by the position of the first spring 31. The first spring 31 has its lower end in contact with the spring seat 29C in the retainer 29, and in its natural state, it is positioned coaxially with the central axis C2 of the retainer 29. Therefore, the center point C3 of the valve body 28, which is separated from the valve seat 26A and now depends on the position of the first spring 31, etc., is located on the central axis C2 of the retainer 29 and moves along the central axis C2.

[0039] In conventional lash adjusters, the central axes of the valve bore and retainer are usually both located on the central axis of the lash adjuster. That is, in conventional lash adjusters, the central axes of the valve bore and retainer are located coaxially. Therefore, in conventional lash adjusters, 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 conventional lash adjusters, the valve body moves linearly along the central axis of the valve bore from the open state to the closed state.

[0040] In contrast, in the case of the lash adjuster 10 of this embodiment, the central axis C1 of the valve bore 26 and the central axis C2 of the retainer 29 are offset from each other. As a result, the center point C3 of the valve body 28 when it is away from the valve seat 26A is positioned at a location offset from the central axis C1 of the valve bore 26. Consequently, when the valve body 28 returns to the closed state, it makes uneven contact with the valve seat 26A for the first time, and then a time lag occurs before it reaches the closed state.

[0041] 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.

[0042] In this embodiment, the valve body 28, when separated from the valve seat 26A, is misaligned with respect to the central axis C1 of the valve bore 26. Therefore, the valve body 28 rises under the biasing force of the first spring 31 at the position where it is misaligned with respect to the central axis C1 of the valve bore 26. Specifically, the valve body 28, when separated from the valve seat 26A, is located on the central axis C2 of the retainer 29, which acts as the guide central axis, and rises along the central axis C2. Subsequently, when the valve body 28 first contacts the valve seat 26A, as shown in Figure 4, it only partially contacts the valve seat 26A and does not completely close the valve bore 26, i.e., it is in a state of partial contact. Thus, until it reaches this state of partial contact, the center point C3 of the valve body 28 moves upward along the central axis C2 of the retainer 29 at the position where it is misaligned with respect to the central axis C1 of the valve bore 26 (see the center point C3 of the valve body 28 shown by the solid line in Figure 4).

[0043] On the other hand, while the valve body 28 is moving from an uncoated 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 direction of movement of the valve body 28 changes before and after the uncoated state occurs in the lash adjuster 10. As a result, the lash adjuster 10 can create a suitable time lag from the uncoated state to the closed state. For example, in the case of a conventional lash adjuster, an uncoated state does not occur in the valve body, and there is no change in the direction of movement of the valve body from the open state to the closed state. Compared with such a conventional lash adjuster, the lash adjuster 10 has a relatively longer time from the open state to the closed state, so more air can be discharged from the high-pressure chamber 27.

[0044] Thus, the lash adjuster 10 has a configuration in which the central axis C1 of the valve hole 26 and the central axis C2 of the retainer 29, which serves as the guide central axis, are offset from each other as a delay portion according to this disclosure. As a result, the lash adjuster 10 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 a result, the lash adjuster 10 can keep the valve hole 26 open for a longer period of time compared to conventional models, and can promote the discharge of air from the high-pressure chamber 27. Therefore, the lash adjuster 10 can suppress the occurrence of air entrapment.

[0045] Furthermore, the lash adjuster 10 has a configuration in which the central axis C1 of the valve hole 26 is offset from the radial center of the bottom portion 18, i.e., from the central axis C of the lash adjuster, as a delay portion according to this disclosure. The lash adjuster 10 can realize the delay portion with only a simple change, which is to change the position of the valve hole from the configuration of a conventional lash adjuster.

[0046] <Example 2> The lash adjuster 210 of Embodiment 2 according to this embodiment differs from that of Embodiment 1 in terms of the configuration related to the valve hole, as shown in Figure 5. Other components that are the same as or equivalent to those of Embodiment 1 are denoted by the same reference numerals, and descriptions that overlap with those of Embodiment 1 are omitted.

[0047] The valve bore 226 of Embodiment 2 has a configuration in which the valve seat 226A is inclined with respect to the horizontal direction. Specifically, as shown in Figure 5, in a cross-sectional view obtained by cutting the bottom 18 of the plunger 12 along the vertical direction at a position passing through the central axis C1 of the valve bore 226, the height of the valve seat 226AR located on one side of the valve bore 226 at the bottom 18 (the right side in Figure 5) is higher than the height of the valve seat 226AL located on the other side (the left side in Figure 5).

[0048] In the cross-sectional view shown in Figure 5, the lower edge 226B of the valve seat 226A, which serves as the opening edge of the valve bore 226, is formed at an angle with respect to the horizontal. This lower edge 226B is an example of an inclined edge according to the present disclosure. As shown in the cross-sectional view of Figure 5, the lower edge 226B of the valve seat 226A forms a straight line that is inclined with respect to the horizontal, from the right end of the right valve seat 226AR to the left end of the left valve seat 226AL. In this embodiment, the angle of inclination of the lower edge 226B of the valve seat 226A with respect to the horizontal is, for example, 8°.

[0049] The valve bore 226 penetrates the bottom 18 in a direction perpendicular to the lower edge 226B of the valve seat 226A. In other words, the valve bore 226 in this embodiment penetrates the bottom 18 at an inclination with respect to the central axis C of the lash adjuster 210. The angle between the central axis C1 of the valve bore 226 and the central axis C (vertical direction) of the lash adjuster 210 is, for example, 8°. The center point C3 of the valve body 28 in the closed state, which is in overall contact with the valve seat 226A, is located on the central axis C1 of the valve bore 226. The central axis C1 of the valve bore 226 is inclined with respect to the central axis C2 of the retainer 29 such 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.

[0050] 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 226A. The tapered surface T slopes upward from the outer peripheral edge of the bottom portion 18 toward the valve seat 226A. 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 226. Due to the inclined formation of the valve hole 226, there is a difference in height in the circumferential direction of the tapered surface T. In the case of Figure 5, the uppermost part of the tapered surface T is the connection part H with the lower end edge 226B of the valve seat 226AR. The lash adjuster 210 is configured such that air tends to accumulate in the high-pressure chamber 27 at this connection part H, which is the uppermost part of the tapered surface T.

[0051] In the lash adjuster 210, from the open state to the one-sided contact state where it first makes contact with the valve seat 226A, the valve body 28 moves along the central axis C2 of the retainer 29 while being biased by the first spring 31, similar to Embodiment 1. In the one-sided contact state with respect to the valve seat 226A, as shown in Figure 5, the valve body 28 is in contact with the valve seat 226AL, which is at a relatively lower position, and away from the valve seat 226AR, which is at a relatively higher position. Subsequently, further biased by the biasing force of the first spring 31, the valve body 28 makes full contact with the valve seat 226A, reaching the closed state.

[0052] As described above, in this embodiment, the central axis C1 of the valve bore 226 is inclined with respect to the central axis C of the lash adjuster 210. This inclination of the central axis C1 of the valve bore 226 is set so that the center point C3 of the valve body 28 in the closed state is misaligned with respect to the central axis C of the lash adjuster 210. With this configuration, the center point C3 of the valve body 28 moves along the central axis C2 of the retainer 29 from the open state to the one-sided contact state, and moves along a different trajectory from the one-sided contact state to the closed state. As a result, the valve body 28 creates a time lag between the one-sided contact state and the closed state. The lash adjuster 210 can suitably discharge air from the high-pressure chamber 27 during this time lag.

[0053] Thus, the lash adjuster 210 has a configuration in which, in a cross-sectional view obtained by cutting the bottom portion 18 along the vertical direction at a position passing through the central axis C2 of the valve hole 226, the height of one portion of the valve seat 226AR on either side of the valve hole 226 on the bottom portion 18 is positioned higher than the height of the valve seat 226AL on the other portion. With this configuration, when the valve is closed, the lash adjuster 210 creates a one-sided contact state in which the valve body 28 first contacts the valve seat 226AL side of the valve seat 226A, before reaching the closed valve state. Therefore, the lash adjuster 210 can suitably generate a time lag from the one-sided contact state to the closed valve state, and can suitably discharge air from the high-pressure chamber 27. In addition, by providing a height difference in the valve seat 226A, the lash adjuster 210 can collect the air in the high-pressure chamber 27 around the valve seat 226AR located on the upper side. This allows the lash adjuster 210 to facilitate the discharge of air collected around the valve seat 226AR located on the upper side.

[0054] The lash adjuster 210 inclines the lower edge 226B of the valve seat 226A and forms a valve hole 226 that penetrates in a direction perpendicular to this lower edge 226B. This makes it possible to easily form a circular contact surface similar to that of a valve seat 26A without a height difference, as in Example 1, even if the valve seat 226A has a height difference. For example, if the valve seat is formed inclined with respect to the horizontal direction in a valve hole that penetrates along the vertical direction, the shape of the opening edge of the valve hole in which the valve seat is formed becomes elliptical. In this case, it is difficult to form a valve seat in which a spherical valve body can contact without gaps. In contrast, if the valve hole 226 penetrates in a direction perpendicular to the lower edge 226B of the inclined valve seat 226A, 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 226A.

[0055] Furthermore, the lash adjuster 210 has a tapered surface T formed on the lower surface of the bottom portion 18. The tapered surface T is formed to slope upward from the outer peripheral edge of the bottom portion 18 toward the valve seat 226A, and the uppermost part of the tapered surface T forms a connection portion H with the lower end edge 226B of the valve seat 226A. With this configuration, the lash adjuster 210 is more likely to accumulate air that has entered the high-pressure chamber 27 at the connection portion H, which is the uppermost part. The connection portion H is the part that connects to the part of the valve seat 226A that closes the slowest between the partially contacted state and the closed state. For this reason, the lash adjuster 210 can effectively discharge the air accumulated around the connection portion H.

[0056] <Other examples> Other embodiments are briefly described below. (1) The configuration of the delay unit according to the present disclosure is not limited to the configuration of each embodiment described above, as long as it can generate a time lag from the state in which the valve body first contacts the valve seat until the valve is closed. The delay unit can be configured, for example, by shifting the position of the center point of the valve body in the closed state relative to the guide center axis of the valve body provided by the guide until the valve body first contacts the valve seat. (2) In the above embodiment 1, the delay portion according to the present disclosure is configured such that the central axis of the valve hole is offset with respect to the central axis of the retainer which is arranged coaxially with the central axis of the lash adjuster. However, as shown in Figure 6, the central axis C2 of the retainer 329 may be offset with respect to the central axis C1 of the valve hole 326 which is arranged coaxially with the central axis C of the lash adjuster. (3) In the above embodiment 2, the opening edge of the valve hole has an inclined edge, and the valve hole is perpendicular to this inclined edge, 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. The inclination angle of the valve hole can be, for example, in the range of 5° to 10° with respect to the vertical direction. Within these ranges, it is possible to achieve both ease of collecting air around the valve seat and ease of manufacture. (4) In the above embodiment 2, a tapered surface was shown on the lower surface of the bottom of the plunger, but this is not essential. The tapered surface may be formed on the lower surface of the bottom through which the valve hole passes, which is not inclined with respect to the central axis of the lash adjuster, as in embodiment 1. The tapered surface may have an uneven angle in the circumferential direction with respect to the central axis of the valve hole, for example. The tapered surface may have an equal 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. [Explanation of Symbols]

[0057] 10,210... Lash adjuster 11…Body 12…Plunger 18...Bottom 19...Peripheral wall part 22... Low-pressure room 26,226,326… valve holes 26A,226A…Valve seat 26B...Lower edge (sloping edge) 27…High-pressure room 28… Valve body 29,329... Retainer (guide) 31…First spring (guide) 226AL... Valve seat (valve seat of the other part) 226AR... Valve seat (one part of the valve seat) C1...Central axis of the valve opening C2... The central axis of the retainer (the central axis of the guide).

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 guide is provided in the high-pressure chamber to guide the movement of the valve body in conjunction with the opening and closing of the valve hole, A lash adjuster equipped with, 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 lash adjuster according to claim 1, wherein the delay portion is configured to offset the central axis of the valve hole and the central axis of the guide of the valve body by the guide until the valve body first contacts the valve seat.

3. The lash adjuster according to claim 2, wherein the delay portion is configured by offsetting the central axis of the valve hole from the radial center of the bottom.

4. The lash adjuster according to claim 1, wherein in a cross-sectional view obtained by cutting the bottom portion along the vertical direction at a position passing through the central axis of the valve hole, the height of the valve seat of 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 of the other portion.

5. 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 4, wherein the valve hole penetrates the bottom portion in a direction perpendicular to the inclined edge.

6. The lash adjuster according to claim 4 or claim 5, wherein the lower surface of one of the aforementioned portions is inclined upward from the outer peripheral edge of the bottom toward the valve seat.

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